(Major spoilers for The New Prophecy, Power of Three and Omen of the Stars.

Crowfeather never really cared about anything but his reputation. He decides to run off with a cat he never knew and comes back. He then decides to use Nightcloud, a cat who has feelings and is living, just so he can fool his Clanmates into thinking he's loyal. He never cared about Nightcloud at all and even went far enough to have kits he didn't want with her. All this was as soon as he rejoined WindClan. She is still a cat with feelings and it's wrong of him to be low enough to use a cat like that. There were other ways he could have proven he was loyal but if anything, I personally think Crowfeather is more loyal to his ThunderClan kin than his own Clan.

"A black she-cat emerged from the group of WindClan cats; Hollypaw recognized Crowfeather's mate, Nightcloud. She brushed her pelt against Crowfeather's. "Take care," he meowed.

Crowfeather gave her ear a quick lick, but Hollypaw noticed that his eyes were gazing into the distance." - Outcast, page 142

Not only did Crowfeather not care about Nightcloud in the slightest, he resented her because he never loved her in the slightest way:

". . . and resentful towards Nightcloud because she was not the she-cat he truly loved." - The Ultimate Guide, page 109

Cats of the Clans also confirms that Crowfeather never even cared much about Nightcloud in the first place, especially since The Ultimate Guide backs it up by stating he resented her:

"After all, Crowfeather took her as a mate to prove he was loyal to WindClan in spite of everything of trying to run off with the ThunderClan medicine cat." - Cats of the Clans, page 54

Crowfeather was never forced to take Nightcloud as a mate. It was his own choice and his only. No cat was actually forcing him to. Crowfeather just decided it was a good idea to take advantage of a cat's feelings because he couldn't be bothered to prove he's loyal to his Clan a better way.

He treats his own son like dirt—worse than Spiderleg because at least he did make an effort to know his kits—and is the main reason he's in the Dark Forest. Crowfeather never praised Breezepelt at all or even bothered getting involved in his life. He never bothered teaching him right from wrong because he left Nightcloud to do all the work herself. If you don't acknowledge your kids positively, they won't learn anything, and not praising them if they do something good, behaviour-wise or not, it just going to make them go to extreme lengths just to get attention. All Crowfeather ever did was snap at his son. He even praised Lionpaw right in front of him.

"This rabbit's so fat it'll feed all the to-bes," Squirrelflight mewed admiringly.

"Well caught, Breezepaw," Tawnypelt purred.

Jaypaw waited for the WindClan apprentice's pelt to flash with pride, but instead he sensed anxiety claw at Breezepaw. He's just waiting for his father to praise him.

"Nice pigeon," Crowfeather mewed to Lionpaw. 

Breezepelt stiffened with anger." - Eclipse, page 21

Crowfeather has never shown concern or a single hint of care for Breezepelt at all. His attitude towards his son was so bad that even Hollypaw, who hated Breezepelt, felt sorry for him.

“Even though he was as bad-tempered as his father and twice as smug, she [Hollypaw] had begun to feel sorry for Breezepaw. Crowfeather treated his son with such scorn that Breezepaw sometimes seemed a loner among his own Clanmates. And Crowfeather hadn't acted like he was glad to have him [Breezepaw] along. He didn't seem proud of anything Breezepaw did.”  - Eclipse, page 13

Lionpaw also felt sorry for him in Outcast for the way Crowfeather was, believing it was because of his loss over Feathertail:

"Maybe losing Feathertail was what made the WindClan cat so bad-tempered all the time. He noticed Breezepaw watching his father with a jealous glint in his narrowed eyes. For once Lionpaw felt a pang of sympathy for him." - Outcast, page 214

Even before they left for the mountains, Crowfeather refused to let Breezepaw say goodbye to his friends:

"I want to say goodbye to my friends first," Breezepaw objected.
"There isn't time!" Crowfeather snapped." - Outcast, page 141

The way Crowfeather treated Breezepelt, refusing to even praise him if he did something good, made him feel isolated within his own Clan. Even if Breezepelt wasn't acting nicely, Crowfeather refused to do anything about it and only snapped at him. Snapping at kits without giving them a good reason as to why they're in the wrong won't make them learn anything from their mistakes. Crowfeather never gave Breezepelt the attention he needed. It got so bad that Breezepelt even felt as though the Dark Forest was a better place to be in than WindClan. Crowfeather never bothered teaching him right from wrong, something he should have done before.

Crowfeather even doubted his son was telling the truth. In fact, he went far enough to believe that Breezepelt would lie about the barrier being damaged which shows a lack of faith in him:

"No damage to the barrier," he [Breezepaw] called.

"Have you checked it all the way round?"

Breezepaw glared at his father. "Of course! That's what Whitetail ordered me to do."

Nightcloud stepped forward. "You should have more faith in our son, Crowfeather." - The Sight, page 293.

Crowfeather went far enough to hurt Leafpool's feelings in Sunrise at the Gathering. He disowned Lionblaze, Hollyleaf and Jayfeather by stating his only son will ever be Breezepelt. Yes, he may have been surprised, but that still doesn't give him the right to say what he said:

"I have one mate," he [Crowfeather] snarled. "Her name is Nightcloud. We have one son, Breezepelt. I don't know why you've come to me with these lies. Go home, and don't come back. Why should I care about ThunderClan cats? You mean nothing to me. Nothing!" - Sunrise, page 296

"It's not true! She's the one who's lying! . . . You mean nothing to me, Leafpool. That moon has passed. My loyalty is to WindClan, and I have no kits other than Breezepelt." - Sunrise, page 306

In Night Whispers, Lionblaze and Breezepelt began fighting and Crowfeather did nothing but watch. If he cared about his sons, he would have broke it up rather than watch them hurt each other over a piece of prey. Instead, Leafpool had to get them to stop. Crowfeather sounds selfish by thinking Leafpool didn't love him just because she decided to choose her Clan over him which was the best option:

"You chose your Clan, remember?" he [Crowfeather] hissed.

"That doesn't mean I didn't love you."

"Maybe you did. But it wasn't enough, was it?" - Night Whispers, page 202-203

Crowfeather also believe he was betraying Feathertail by falling for Leafpool too soon. In my opinion, I don't think Crowfeather ever truly loved anyone after Feathertail's death and tried filling in that empty hole in his heart to try forgetting about her. I think his love for Leafpool is just an echo for Feathertail because he constantly believes Leafpool is like Feathertail in a way. He felt horrible for loving a cat besides Feathertail.

"And how much I hate myself for feeling that way about another cat so soon after Feathertail's death? I loved her, I really did! How can I love you too?" - Starlight, page 311

Crowfeather seems to have forgotten he chose his warrior name after Feathertail specifically. He only keeps causing more trouble for himself and doesn't bother trying to make things better without hurting other cats in the process. In my opinion, Crowfeather shouldn't have a mate. He keeps hurting cats and breaking their hearts--himself included.

Tallstar: Crowpaw has served his Clan with loyalty and bravery. He should have received his warrior name long ago, but the tragedies of the past moons have prevented this. Tonight, if Stoneteller will do me the kindness of letting a Clan ceremony into his Tribe's home, I wish to honour Crowpaw's great skill and courage by giving him his warrior name.

Crowpaw: May I ask something, Tallstar? I would like to choose my own warrior name. If it is all right, I wish to be known as Crowfeather. I wish to keep alive the memory of... of the cat who did not return from the first journey.

Tallstar: A noble request. Very well. I name you Crowfeather. May StarClan protect you and accept you as a WindClan warrior in life as well as after. - Crowpaw's warrior ceremony, Dawn, page 316

Even after Feathertail died, Crowfeather always blamed himself. I think Crowfeather tricked himself into believing he loved Leafpool just because he could see Feathertail in her personality-wise.

"It's my fault. If I'd refuse to come back into the cave, she would have stayed with me." - Moonrise, page 272.

A few other examples where Crowfeather still misses Feathertail are shown throughout Dawn and Outcast:

"And I--I will go. I would like to stand again in the place where Feathertail lies." - Outcast, page 141

"Crowfeather had wandered away from the rest of the group and was sitting with his head bowed beside a heap of stones on the other side of the pool, underneath a twisted tree. "What's Crowfeather doing?" Lionpaw asked.

"That's where Feathertail is buried," Tawnypelt explained.

Lionpaw stared at the small grey-black cat crouched beside the pile of stones. "Why is Crowfeather so upset? They weren't even in the same Clan. . ."

"Crowfeather loved her." - Outcast, page 214

"He was sitting with his head bowed beside the low mound of rocks that marked Feathertail's grave."  - Dawn, page 317

Crowfeather was still a very young cat; he didn't give himself time to grieve and move on properly before he suddenly decides he loves Leafpool. He rushes from one cat to another within a short span of time; he fell for Leafpool not long after Feathertail died and moved onto Nightcloud (though didn't love her) and got her pregnant in barely a moon after breaking his relationship with Leafpool off.

In The Last Hope, after clearing disowning his ThunderClan kits right to their faces and making it clear he wanted nothing to do with Leafpool, he suddenly loves them and doesn't regret a single thing? He also states he never hated Breezepelt when he made it obvious he never liked him in the first place. Many cats had even picked up on that:

"I never hated you! That's what you were determined to believe. And Nightcloud encouraged you." - The Last Hope, page 308.

He then blames it on Nightcloud to try making it seem as though he did no wrong when in fact he was never even acting fatherly towards Breezepelt. All he ever did was act bitter and harsh towards him no matter what he did. He made Breezepelt's behaviour worsen. Crowfeather never even acted as if he ever cared about Breezepelt while Nightcloud tried making an effort to care for him. For all we know, Crowfeather could be making stuff up to make himself seem innocent, or Breezepelt could have picked up on that even more from the way Crowfeather and Nightcloud acted towards each other. Crowfeather annoyed me even more by saying he never regretted anything to Leafpool even after how horrible he had acted towards her and his ThunderClan kits: 

"It was never meant to be. I don't regret anything. Nothing at all."  - The Last Hope, page 309

All Crowfeather ever did was mope about because he couldn't have Leafpool or Feathertail. He never even bothered to actually know his family, or even acknowledge them positively. I get Crowfeather was in love but moping about isn't going to solve his problems. That should not excuse the way he treats Nightcloud and Breezepelt. He was still a complete jerk to them and even Leafpool, Lionblaze, Jayfeather and Hollyleaf, yet he turns around and says he loves them after he made it clear he never wanted to know them anymore.

Crowfeather shouldn't have taken a mate if he's just going to either break their hearts or don't care about them at all. Even if he and Feathertail were together, he still could never understand her. Feathertail is too old for him anyway--in a mental sense, not physically--because she had to grow up quickly. She had traumatising events, something Crowfeather could never understand as he had a normal apprentice's/kit's life.


She had to grow up quickly because: her mother died giving birth to her and her brother, RiverClan and ThunderClan nearly went to war over them, their father was exiled and rejoined ThunderClan, they were nearly killed for being half-Clan, and Stonefur was killed defending them right in front of their eyes. Prior to Midnight, Crowfeather only ever caused trouble like a normal kit would and had an easy life. He never had his loyalty questioned until he decided it was a good idea to run away with Leafpool. Talking about them running away, it was Crowfeather who suggested the idea first:
 

"Crowfeather said the same thing: "We can't go on like this, Leafpool. We'll never be together unless we leave our Clans . . . It's the only way. Will you think about it, please?" - Twilight, page 240.

He even knew it was wrong to love Leafpool yet he still ends up running away with her. What's worse is the fact they barely knew each other and only confessed their "love" that came out of nowhere when Crowfeather saved Leafpool:

"I did it," Crowfeather whispered. "I saved you."

The air between them seemed to crackle like lightning. Trying to lighten the atmosphere, Leafpool commented, "I must be the last cat you wanted to save."

"Is that what you think?" Crowfeather's gaze burned into her. "Don't you know how I feel about you? And how much I hate myself for feeling the way about another cat so soon after Feathertail's death? I loved her, I really did! How can I love you too?"

"Me? But--"

"You walk in my dreams, Leafpool," Crowfeather whispered.

"No . . ." Leafpool breathed. "You can't love me. I'm a medicine cat." And I love you, she thought desperately. But she knew that she did, more than she ever thought possible. To hear that Crowfeather loved her too was what she wanted more than anything else." - Twilight, page 309-310

Leaving his Clan for a she-cat he knew is not loyalty, and is selfish. They're both at fault here, for agreeing and abandoning their Clans. What if WindClan was in just as much danger as ThunderClan was at the time? Crowfeather would have happily walked out on his Clan and some of his Clanmates could have died. It was reckless and stupid to do. Crowfeather was actually lucky Onestar decided to take him back in and keep him as a warrior. In fact, he was just lucky to have been given a chance at all, and he basically threw it away by taking advantage of a she-cat's feelings. Even if Nightcloud was the worst cat in the Clans, it's still wrong to use someone, regardless of who they are.