heh....I don't really know the worst adaptation movie since I didn't really read the comics, but I do know enough about the original characters that I get angry when they change them for the movies. For example, Rogue from Xmen. Her original comic and cartoon appearances, she kept the powers she borrowed. She didn't have the ability for a few minutes, it was permanent (she still hated her power, but it was a permanent thing, not a temporary thing, and she wouldn't have gotten rid of her power with the 'cure'.)
That's kind of my pet peeve is when they get the characters wrong, not necessarily the entire movie (if they get the whole movie wrong then it's something to laugh at and never watch again, not something to get mad over)