First: The short version
Negasonic Teenage Warhead is a mutant teenager from the Deadpool movie who can blow up things. She's sullen, sarcastic, moody and dresses mostly in black to hide her X-man uniform. Boom. Short version.
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The long version
Negasonic comes from the Deadpool movie which is based on the convoluted X-men movie universe which is own by Fox even though Marvel would probably like to pry the licensing rights from Fox's grubby little hands.
This particular universe is based on the X-men comics. In this fictional world there are a subset of humans with mutations that give them fantastic powers. Some can fly, some can duplicate, some get iron skin and (on the more sucky side of the scale) one mutant got an extra six feet of skin. Some of these mutants are good, some of them are bad and the rest of the world pretty much hates these guys with powers because they fear change. However unlike the Marvel Comics universe the X-men are a universe onto their own. (Captain America? Tony Stark? Who's that?)
On the good side is the X-men led by Professor X (Either McAvoy or Stewart depending where you are in the timeline), Wolverine and so forth. On the bad side is Magneto (sometimes), Apocalypse (Which I haven't seen yet. And may not.) and Mystique (Sometimes good-sometimes bad depending on Jennifer Lawrence's popularity)
Because of the "Bad" mutants who use their powers as they see fit, most of humanity despise the mutant population and don't appreciate the X-men who are trying to do good.
Now in this universe is a character named Deadpool who is not a mutant but a mercenary who got cancer and subsequently got injected with some Wolverine "DNA/Blood" and got tortured until he gained a healing factor which transformed him into a hideous looking human being. Taking on the masked identity of Deadpool, Wade Wilson went after the people who gave him his powers. Where and when this happens in the X-men universe timeline... who the fuck knows. It's been rebooted and going through a whole thing with Brian Singer. For now I'm saying Deadpool occurs around 2015-2016 and rolling with it.
The character herself:
Teenage Negaonic Warhead originally appeared in Grant Morrison's X-Men comic however she didn't have a huge role. In that particular version she had some telepathic and precognitive powers but she was quickly killed off in Genosha, came back once as a telepathic illusion and then was resurrected briefly by a comic book company event and then quickly killed off again.
For my FH I will be ignoring all of that canon as it doesn't fit her appearance in the Deadpool movie other than keeping her true name (Ellie Phimister). That won't matter much because Negasonic will stick with her code name as her identity because that's how she rolls in my mind.
Negasonic is a little over five feet tall, with a shaved head (think Sinead O'Connor if you are old enough to remember her), multiple piercings, wears black clothing and is pretty much your standard sullen teenage goth girl with mutant powers. While in the comics she had psychic powers in the movie Negasonic is pretty much a living bomb. She possesses the ability to channel energy throughout her body and use it to propel objects or people. At lower levels she could move a car. At maximum power, she was able to level an entire scrap yard and destroy a hellicarrier an aircraft carrier. Since Using this type of power may be bad for the dorms, I won't be using her powers unless it's a condoned plotty thing.
Personality wise, she is a sullen kid who doesn't talk much except to make sarcastic jokes/mean things. She almost never smiles or laughs unless it's at the expense of another person.(For example: When Deadpool is getting his ass kicked by Colossus? Hilarious!). If another person is being stupid or annoying, you're pretty much dead to her and either will be ignored in sullen silence or earn a nasty or flippant comment.
Fun right?!
And that sums up Negasonic.
Questions? Comments? Pie?