Tools of Characterization
Characterization in Deadpool
Actions
When it comes right down to it, comic book movies are action movies, and the principal players in Deadpool are characterized accordingly. What they do matters.
At one end of the spectrum, we have Ajax. He's cowardly sadistic. He has super powers, but he prefers to torture others using science and a variety of contraptions, each more lethal than the next.
At the other end of the spectrum sit Colossus and Negasonic Teenage Warhead, both of whom use their super powers for good and to defend what's right. Deadpool's somewhere in the middle, probably a tad toward the Ajax end of the line. He can be downright brutal, but only if he feels the recipient deserves it. The keyword there is "he," since Deadpool's actions are governed by their own unique moral code that was created exclusively by Deadpool.
Finally, there's Weasel. He's cautious and practical. When Wade first shows him his disfigured mug, Weasel immediately jumps on the idea that Wade should make horror films. After that gets shot down, Weasel's the one who points out that Ajax thinks Wade's dead and helps his pal formulate a revenge plot accordingly. He helps Wade stockpile guns and ammo for the big fight, and when it's time to head into battle, he—well, he promptly bows out like any reasonable, non-mutant might. Weasel may not want to dance with a mutant psychopath, but his actions show that he does care about Wade. Exhibit A is that stockpile of wheatgrass he suddenly has behind the bar at Sister Margaret's.
Direct Characterization
Given Deadpool's fondness for breaking the fourth wall, it should come as no surprise that we learn a lot about him through direct characterization. He tells us directly that he's just a bad guy who gets paid to mess up worse guys and that he's most certainly not a hero. He gives us insight into his character when he shares his belief that "life is an endless series of train-wrecks with only brief, commercial-like breaks of happiness." He even tells us that he enters the Weapon X program not to save his life, but to save Vanessa's. By the end of the move, there's not a whole lot we don't know about Deadpool's character because the guy can't stop talking.
Thoughts and Opinions
Deadpool and Colossus agree on very little. Colossus thinks mutants have a responsibility to use their powers carefully and with a purpose. Deadpool, not so much. Colossus wants Deadpool to make "good" decisions and be heroic. Deadpool would rather cut his own hand off and dive into a garbage truck. Colossus views things in black and white, and Deadpool sees a whole lot of gray. Neither seems willing to change his opinion. Deadpool, or Wade, is similarly hardheaded when it comes to his cancer diagnosis. He's cynical and fatalistic, while Vanessa is characterized by her hope and her readiness to fight.
Type of Being
Deadpool and Ajax may be mortal enemies, but the fact remains that they're both characterized by the fact that they're mutants. Being a mutant that can't feel pain or emotions has turned Ajax into an evil sadist. Being super-powered and super-scarred turned Wade into Deadpool, a man with a singular mission: to do whatever it takes to get Vanessa back in his life. Meanwhile, Colossus and Negasonic Teenage Warhead are also mutants, which makes them peers and provides them with an understanding of Deadpool, even if they don't always dig the uber-violent way he uses his mutant abilities.