3. Bruce Banner & Betty Ross (The Incredible Hulk)
Lets go with the Marvel Cinematic Universe version here. Our introduction to Bruce and Betty is fairly early on, in the opening sequence to The Incredible Hulk. Unfortunately, about ten seconds into that montage Bruce hulks out and destroys half of Bettys face. Not the greatest way to start things off. Throughout the course of the movie, Bruce and Betty rekindle the romance that ended when her father chased him off. Unfortunately for Betty, this involves harboring a fugitive, not to mention putting her life in danger every minute she spends in said fugitives company. Is it worth it? Apparently so, because before Bruce showed up she was dating a neurosurgeon with a nonexistent sense of humor, whom she literally just walked away from to get to Bruce. It seems a little one-sided. Betty gives up everything her career, her belongings, possibly her freedom for Bruce, and in return she gets... the constant threat of death. And yes, he saves her life a few times along the way, but hes always saving her from a situation that he is indirectly the cause of to begin with.
How It Ends: In the end, they go their separate ways, because keeping regular company with a rage monster is evidently not a good idea. The exact nature of their relationship is left ambiguous, until, of course, we run into Bruce again in The Avengers, where there is an interesting contrast between Banner and Thor. Whereas Thor comes back from a whole different planet and makes it a point to inquire about Janes well-being, Banner whos back in the country for the first time in who knows how long doesnt even mention Betty. Not even in passing.