"I'm super strong, I have god powers, elements, control over darkness and I regenerate." 

*Okay whats your species?* 

"*Names a species that is incapable of doing that*" 

*.....Right.*

This is a sue/stu trait that really pulls my hair. When you first start making a character, likely one of the first things you decide is the species. A species is what your character is and will define a lot about them, and with a species comes a list of traits. Let's use my species Zoreian for example. 

Zoreians are a believed to be extinct species of puffball (piyan) that showed up briefly between the years 50467-50489EC in West Novaton planets before the events of the war killed them off. From it two Starwarriors survived belonging to the species, Eveah'tal and Dalh'ikahno, and after the third period of the war Dalh'ikahno was the only one believed to continue existing when Eveah'tal and their daughter Fea'iteia were shot and killed in battle. That aside, skill wise, Zoriean are fairly powerful. They have the ability to produce fire from any part of their body that has pores. Their sweat is fire resistant, which allows them to be mostly fire proof, but not 100% so. All Zoreians can walk on water, as a plunge would mean being too wet to make fire for a few hours, as fire is a main protection that would be bad, so swimming is not a excessive thing for them. This ability is used for fishing, while a pair of either feathery wings or webbed wings allow them to fly over water if they don't want to risk getting wet. Neither of these powers are considered 'super powers', and besides that they have no other abilities. Claws and scale like growths on their tails are used as tools and as a means to defend themselves. The use of swords, guns, knives, and other things of the sort are practically nonexistent to them as claws make them too clumsy to hold such things. 

Here we have a few traits, a Zoreian will always have claws and a uniquely shaped tail blade, they sharpen this blade to their liking. They can produce fire from their core, and walk on water. All Zoriean have wings, although due to their tail, which is often very muscly therefore heavy, they are not fast fliers. If I made a Zoreian and gave them a sword, the Zoriean would fail epically when it comes to using it, and even with training they'd be awkward. So if I wanted a sword master character, or a puffball with a gun or any other super powers, a Zoreian would not make a good species choice. Finally comes the nature part. Zoreian are easy going, friendly, very passionate and protective. They heavily dislike violence outside of playful wrestling or defending what they believe in, and will never actively seek out to harm others unless that other has hurt them or their loved ones personally. If I wanted to make a character with a violent temper, an assassin or murderer, or an monotone character, a Zoreian would not be a good choice as that goes against their justiciable nature. Disregarding a species traits is not only confusing, but it's practically throwing their identity as a species away.

What I'm saying is before you make a character, try not to choose their species first, but rather make their personality first. Find out what kind of character you want then pick what they are. It's not always bad to have a the character have a weird colour or perhaps they don't follow the personality of the species, the odd one out is always fun, that being said don't give the characters a power they should be incapable of having. Not only does it make the character a stu or sue, it's just illogical and unreasonable.