This is not about animal cruelty but it is about Ultimate Fighting. I am not trying to romanticize violence.

Your past was something you didn't like to discuss, not even with your boyfriend; Clint Barton, AKA- Hawkeye. He knew that you used to be involved in ultimate fighting, he had seen your old scars, but he never knew the extent. You were part of an illegal fight club. The money was good, and you used to get a sick thrill from the battles but you eventually had to quit. At first, it was just simple street rules; any bone-breaking, spine-crunching, blood-shedding move was allowed. It was hard to keep your injuries a secret, but you found a way. Then the Ring Leader, (you never knew his real name), decided to combine this blood-sport with ultimate wrestling, causing deeper wounds and further violence. It wasn't until the fight club became more like 'Thunder-Dome' that you left. The rules were always simple- anything goes but don't kill your opponent. The Ring Leader found out, the more vicious the fights, the bigger profit he could make. Fearing for your life, you never stepped in the ring again. Luckily, anonymity of the fighters kept you safe.

...

You had received some intel on a fight that was happening soon. You knew it was a bad idea to investigate it yourself, but the allure of your old battlefield was too strong. Sure you had your fights, as a part of S.H.I.E.L.D but you had to hold yourself back. Fitting an old Halloween mask with a camera, you crept out of the Avenger's Tower. Clint was away on a mission and wouldn't be home until the following day, so you weren't worried about him catching you. You slipped in unnoticed by any of the fighters. There were already two men engaged in a brawl, surrounded by spectators and challengers. You made sure to get footage of them and the cruel weapons at their feet. Some of them weren't even proper weapons; just tools for inflicting as much pain as possible. The sound of connecting skin and the smell of blood brought back memories.

"Hey." A chubby woman approached you.

"You here to fight or place a bet?" You didn't have any money to bet with and if you didn't answer, your cover would be blown.

"Fight."

"Follow me then," she said, cocking her head to indicate the direction to go. The woman led you to the locker-room where the fighters prepared. One thing about these battles, they were often held in old and abandoned factories that could wash away the evidence. You took off your jacket, leaving you in your sports-bra and sweat-pants. They wouldn't bother asking you about your mask, as most people there also were wearing them. You stepped in the ring, the roar of crowd making your muscles twitch in anticipation. The girl you were up against was shorter and leaner than you were, but you knew better than to underestimate her. You turned your head, making sure to catch the Ring Leader on the cat-walk above.

"Ready...?" You raised your fists and she raised hers.

"Fight!" The girl charged at you but you had anticipated her move. You dodged her attack, grabbing her waist and throwing her down. She jumped up, landing an uppercut on your jaw. You stumbled back but she gave you no time to recover as she launched at you once more, knocking you over. Shaking off your initial shock, you flipped her over. Her arms slipped behind you, one hand clawing at your back, the other at your neck. Her fingers hooked in the back of your mask, ripping it from your head. The girl kicked you off her and you stood on unsteady legs. There was a murmur through the spectators as some of them recognised you.

"Time out!" the Ring Leader called. You tried you hide your face, but he had already recognised you.

"It seems... that we have a special guest! Meet one of the best fighters this club has ever seen!" The audience cheered and a wicked grin spread across the Ring Leader's face. He was pissed when you had left, now was his chance to exact his revenge.

"Would you like to see her against a tougher adversary?" The crowd roared.

"Hey, what about me?!" the girl shouted.

"Don't worry my dear; you'll still get a chance to fight for glory. But for now, would you mind tagging out?" The Ring Leader motioned for a rather burly man to take her place. He held up his large hand to signal for her to tag him in. You had faced guys bigger than him as part of your training, and your past experience had taught you to expect anything. This guy was basically a walking wall of flesh, so you knew your small fists would do little to damage him. You had spotted a pair of spiked brass-knuckles but you were reluctant to use them. The only thing you could do was evade his attacks, all the while; your mind was formulating an escape plan. Something you found eerie about this man is that he remained silent. He made not so much as a quip or insult just angry grunts. You had failed to notice your mask on the ground and you slipped on it, sending you flat on your back. The large male stood over you and placed his boot on your throat. Your fingers curled around his foot, desperate to relive the pressure, but you blacked out.

...

You woke hours later with a pounding in your head. Groaning, you sat up, trying to make sense of your surroundings. You were in some kind of brick basement with the windows boarded up. The only light in the room came from a flickering bulb in the centre. When you're vision had cleared, you saw the Ring Leader beaming down at you.

"You're really ugly when you do that," you sneered. He laughed in response, sending a chill down your spine. You couldn't allow him to know how scared you were.

"You can insult me you all you like, but I still have you. Just like the rest of them, you returned to the club." You looked around to see a few familiar faces, all of them blank and emotionless. He snapped his fingers and the large man from before dragged you to your feet, pulling you into a bear-hug.

"What did you do to them?!" you hissed.

"You see my dear, when my fighters began leaving, I realised I had to do something..." he said, taking out a syringe. "People are too soft hearted for this line of business. I need something more... animalistic." You had no time to register what his words meant before the needle was jabbed into your neck.

...

Clint arrived earlier than he had anticipated. Excited to see his girlfriend, he ran to their shared room. He hadn't expected her to be there but it was just a thought. Clint looked around all her usual places around the Avengers' Tower, but she wasn't in any of them. When he heard the sound of the punching bag getting a workout, he was filled with hope, but it was quickly diminished when he saw Steve Rogers.

"Have you seen ____?" Clint asked.

"Haven't seen her... since last night. I think she... had a mission," he panted, continuing to beat the punching bag. Maybe someone at S.H.I.E.L.D would know where she went. Clint thanked him and left.

...

Maria Hill greeted him with a serious expression.

"Recently, S.H.I.E.L.D had received a tip about an illegal fight ring and Agent ____ had gone to investigate. Last night, we were sent this surveillance," she explained, holding out her tablet for Clint to look at. He watched from her eyes the savage event take place until the camera was flung away. Although he couldn't see what was happening, he could hear. Maria took her tablet back and stopped the footage.

"It continues for a while, but we have reason to believe that Agent ____ has been taken. We went to the last place she was seen but all that we recovered was her jacket." Maria brought up an image on the screen, a file matching a still from the video.

"The man in the picture is Cornelius Ryan. He's a promoter for various clubs around town but we've had reason to believe that he's been running underground fight clubs." Clint knew that his girlfriend had a history as an ultimate fighter, but he didn't know how deep she was in until this. 'Oh, babe. What have you done?' he thought.

...

Clint sat on the rooftop looking into the old building. Luckily, ____'s beacon was still active, so they were able to track her. S.H.I.E.L.D wanted to wait until another fight took place, much to the objections of Hawkeye. He could see her through the special binoculars in his hand. She was engaged in a fight with a man, twice her height and three times her build. He could see deep wounds on her face and along her body. ____ had strange gloves on her hands and it wasn't until she landed a hit, that he saw what they did. Blue electricity sparked from them with every blow she made. ____ went for a right hook but her opponent picked up a baseball-bat, wrapped with barbed wire and swung it against her side. With her body open, she had no way of stopping the brutal strike. Clint flinched at the sight. It was like something out of a gladiator film. ____ was knocked off balance and the larger man raised the bat over his head, ready to bring it down. On instinct, Clint let fly an arrow, hitting an alarm. The confusion made the big guy stop momentarily as smoke filled the room. Troops swarmed in adding to the chaos. In all of the bedlam, Clint lost sight of ____.

"Dammit!" Clint swore. Not only had he lost sight of the target, he had lost sight of his girlfriend.

...

The Ring Leader let out a loud groan of frustration, causing the fighters to growl as well.

"I knew it was a matter of time before the feds found out! The only question is; who are they?" The Ring Leader's musings were cut short by the door being kicked down. The man let loose an arrow but on instinct, you jumped, protecting you master. The Ring Leader smiled, pleased at your quick reflexes.

"So, they sent Hawkeye. That must mean either the Avengers or S.H.I.E.L.D." Hawkeye could only watch in horror as you pulled the arrow out of your side. Your body screamed in protest, but your mind was impervious to the pain. The Ring Leader could see the discomfort on the hero's face.

"A special serum I acquired," he explained. "You see, I found that human beings have too much free will. Dogs however; are obedient servants. It's like having my own little pack of human pitbulls. They'll obey any whim I command, they're immune to pain..." His lips curled into vicious grin.

"And just like dogs in an arena, they'll fight until they're dead." The Ring Leader had noticed Hawkeye's focus on you and placed a hand on your head.

"Why don't you take this one my pet?" You snarled, teeth bared and charged at Hawkeye. He quickly cast his bow aside, and readied himself. You let fly a barrage of punches, but he blocked all of them. Using a move you had never done before, you landed a kick between his legs. Hawkeye lost concentration and you were able to knock him off his feet. You straddled him, hands tight around his throat.

"____, it's me!" he choked. Your grip loosened a little.

"Hawk...eye?" He could see your face struggling to comprehend. You started to shake as the first signs of pain started to flow through you.

"Yes, that's it! Fight it!"

"F-ight?" The glazed look returned to your eyes.

"F-first r-rule of fight club; n-ever speak of it," you recited. In way, your brain was trying to protect you.

"Second rule... no mercy!" your grip tightened. Hawkeye tried to pry your hands away. Suddenly, a shot was fired into your hip. You flinched and stood up, stumbling to the middle of the room.

"Widow no! The fighters are under some kind of mind control!" he roared. You trembled, staring at the fresh injury. Tears filled your eyes as the pain hit you. You let out a howl of agony and collapsed, body convulsing as you went into shock. The Ring Leader took out a pistol.

"If you're hurting that much, I'll just have to put you out of your misery!" He aimed, but an arrow flew through his neck.

"Target secured," Hawkeye said into his earpiece. He ran over to you, taking your quivering, broken body into his arms as agents entered the building. With no master to answer to, the other fighters did nothing.

"Come on babe, stay with me."

"Clint," you whimpered.

"It's alright ____. I've got you." That was the last thing you remembered before you passed out.

...

You could hear the sound of a steady beep. You forced your heavy eyelids to open. You could now see that you were lying in a hospital bed. Turning your head, you saw your boyfriend Clint. He was sound asleep in an uncomfortable chair, his hand limply held yours. Stiffly, you squeezed his fingers, still too sore to do much else. He stirred and opened his eyes.

"____! You're awake." Clint carefully hugged you and kissed your forehead. "I was so afraid I was gonna lose you."

"How long was I out?"

"A few weeks," he replied. "S.H.I.E.L.D. was able to free the fighters from their mind control."

"And the Ring Leader?"

"Dead." You were relieved. Clint gently stroked the uninjured side of your face.

"Why didn't tell me the truth about your past?"

"Why don't you tell me about when you were an assassin?" you retorted bluntly. Clint opened his mouth to respond, but closed it again.

"I'm not proud of it Clint. Not in the slightest. I don't ever want to go back," you sobbed.

"You don't have to," he whispered, placing a tender kiss on your lips. Before, you'd have to endure the suffering on your own, scared you'd never live to see another day. In Clint's arms, you felt safe. You were a strong woman and could take care of yourself, but you knew he'd protect you. Clint would rather die before getting you in that situation again.

"I love you," he mumbled into your hair.

"I love you too," you replied. As it turned out, even the wildest pitbull could be tamed by the right handler.