Holmes and Moriarty (never read the books) etc.
Moriarty in the books is barely even a character at all. He's someone who Holmes suddenly starts talking to Watson about in the final volume of the first run of the series, stating he'd been tracking the guy and has finally got him cornered. And then, when they go after him, Holmes and Moriarty suddenly go for each other's throats and both go over a waterfall. I don't think the guy even had a single speaking line. All we know about him came from things Holmes said about him.
I say first run because Conan Doyle originally intended to kill the character off and end the series with this, but it got brought back a few years later with Holmes having "miraculously survived" his tumble over the waterfall.
EDIT: Actually, while more modern takes on the material have greatly increased Moriarty's role, if you look at only the original content, it's presented in a way where some wild fan theories could even posit that maybe Moriarty was in league with Holmes the entire time, and he was just some guy Holmes had hired to help him fake his own death. I mean, his return at the beginning of his next series even has him say the only reason he faked his death was so he could get an entirely different major crime boss he'd been going after (I forget the guy's name, but it was not Moriarty.) So, it seems entirely possible Moriarty could have been a co-conspirator who was helping him fake his death so Holmes could get this other guy.
Seriously, Watson's only reason to believe Moriarty was a bad dude was because Holmes told him he was just earlier the same day, and before this Moriarty never even appeared once anywhere in the entire series, and then he never appeared again afterward either.
