Every now and then a character comes along who can ruin the story for you. Usually, for me it's a villain with a very specific set of criteria; they have to be annoying and evil, and for them to really just fuck up the story - never quite get what's coming to them. No satisfying comeuppance. Fate happens and you find yourself sitting there going; "That's not how I would have done that. More suffering, please."
Quentin Tarantino is a good example of this, and in typical fashion, also a bad example of this. In Inglourious Basterds and Pulp Fiction, Zed and Col. Landa really get what's coming to them in a very solid, somewhat drawn-out way, really satisfying for the audience, and giving us the - again, classic - "I'm gonna get medieval on your ass" from Marcellus Wallace. On the other end of things, of course, there are the twin examples from the Kill Bill suckfest, where the man who took part in hundreds of systematic rapes of the Bride is quickly crushed in a door (not good enough) and then Bill himself's death, which is just too predictable and dumb after you've waited two movies for it.
Others? Dolores Umbridge comes close to not having enough comeuppance, until you realize that she is not only publicly humiliated by the Weasleys, but probably gang-raped by centaurs. I personally found the deaths of both Bellatrix LeStrange and Voldemort pretty unsatisfying, but that book was so riddled with fucking death, I just wanted to be done with it. Emperor Palpatine from Star Wars? Not nearly enough - would have liked to have seen the fear evaporate from his face along with his skin or something. Darth's supposed redemption story is pretty weak, too. Belloq and the Nazis at the end of Raiders of the Lost Ark are good - God explodes their faces with death angels due to their arrogance? Awesome. Ideally, you (Okay, I) want whoever the villain is to get the full Mussolini, dragged out, exposed, flipped upside-down and murdered in the town square.
Comic books, TV series (including soap operas) and horror movie villains are a special case inasmuch as since they have to come back for something else later, they never quite die. The Joker, Dr. Doom, Sonny Corinthos, Arvin Sloane, Jason Voorhees and Michael Myers get punished and seemingly killed a bunch of times, but they have contractual obligations, so they end up coming back. This is why I typically don't watch horror movies of the slasher genre - I find them unsatisfying. Too many pointless murders, not enough scale-balancing. I can only sporadically watch General Hospital with my wife because the cycles wear me out. Sloane got his, and if you stick around reading comics long enough, you see the villains really get theirs a bunch of times, and it fuels the rage behind their returns.
Building to this, then: I hate Lucy. Hate the bitch. Lucy is an opinonated loudmouth bully, massively insensitive, lazy, self-centered, obsessive, pathological and stupid. It's like we had 60 years of practice for Sarah Palin before she showed up. Lucy ruins Peanuts for me, just a little bit. I typically skip the ones with this insulting name-caller in them, and only half watch the specials as a consequence. I stick to Snoopy jokes and Pig Pen and ones with just Linus and Charlie Brown. If Charlie Brown represents hope (and being a sucker) with the football thing, Lucy represents the world looking to fuck you while wearing a pretty dress every single time. If Charlie were smart, he'd simply kick Lucy. For a field goal. Lucy's uncivil, she's uncooperative, has the ego to charge people for her shit advice, and it's pretty clear that she has low self-esteem that she deals with by screwing with the lives of others. The bullies should have always been the voiceless, faceless adults in the world of Peanuts; having this predatory ass come from within the fold of children might be realistic, but she never really seems to get hers - not enough - and I find it unsatisfying, to say the least.
So - your examples are welcome - whose comeuppance and/or lack thereof works or doesn't work for you in your favorite fiction?

