Deadpool is Wade Wilson's code name. The character from the comic is played
by the actor Ryan Reynolds in the movies. Deadpool is completely insane
and violent, but with a great sense of humor and he cares about others.
He's a super soldier experiment turned rogue. He agreed to it to survive
his cancer because he wanted to live for his lover.
His cancer might actually be a mutation. Instead to cure it his super healing
abilities regenerate his cells faster than he'd die, making him disfigured,
messing with his brain... and he became basically immortal. He's actually
aware that he's a character and breaks the 4th wall to speak with the audience...
So being insane might actually be being more aware of anybody else, and
everyone would have a hard time coping with that. Humor is a great way,
and his wicked mind has an endless supply of it.