My two favourite murderous clones, Laura Kinney and Kaine, X-23 and the Scarlet Spider!
Kaine is a clone of Spider-man, made back when Spidey was going through this clone phase. Kaine was an imperfect clone and was dying pretty much from birth... Y'know, faster than usual. He was in constant pain, scarred, and constantly aware of his fate. He was rightfully angry. The anger turned him violent, and somewhere down the line he started killing for money.
Move forward to something I know about, Kraven's family wanted to bring Kraven the Hunter back to life, after her swallowed one of those ridiculously long hunting rifles (I assume, the image is funny to me) after screwing with Spider-man in fantastic ways, but to do so they needed to sacrifice Spider-Man. Kaine put on his shiniest tights and went out to either beat them or take Peter's place, and he succeeded at the latter, being killed for Kraven to come back as an undead, unfeeling, psychopath.
Skip forward a few months and Kaine was dug up and brought back to life. It was a very short death, even by comic book standards. He was turned into a spider monster, then turned back, and helped Peter beat another villain, and we have Spider Island. Kaine immediately starts running, because he's a wanted man (the previously mentioned "killing for money"), and took Spider-Man's stealth suit (he has one of those) with him to Houston, where he takes a shitton of money from some criminals, saves a girl's life, and decides to stick around for a day or two. It's around here that we learn that Kaine isn't dying anymore, by his word and the fact that his scars are gone. A whole whack of stuff happens in Houston that ends with him being responsible for an illegal immigrant that would be murdered the second she appeared in Mexico, and the police asking him to stay as their super hero. Kaine set up shop, and is begrudgingly saving lives.
X-23 is the character that got me into comics, I've explained her story before.
