There are even down right wicked villains, with no redeeming qualities, that still are liked by readers. The Joker, for example, is the personification of an Anarchist. Nothing he does is redeemable, but he still manages to be a reader's favorite villain.
There are of course the villains that simply no one cares for. Dime a dozen crack pots, with a scheme or an ability -- they challenge the hero, but ultimately are just background filler.
No - the "bad villain" I'm talking about is Doctor Light, foe of the JLA and Teen Titans. I hate this character. It's not that he's not challenging, or complicated, or fits with the story. It's because he crosses a line that readers just don't like, and there's a collective shiver every time he comes up. This is, of course, because he was revealed to be a rapist in DC's "Identity Crisis" mini-series.
The events of Identity Crisis certainly upped Doctor Light's profile. Readers all remembered that he existed, because he has been down played for years as an inept "dime store" villain. Now, I'm not knocking Identity Crisis - it was a great and very well written story. But it fundamentally changed Doctor Light. Yes, he became more dangerous and more of a threat - but he also became the villain readers just don't want to read about. I was delighted that the Spectre recently killed him. Sadly, death hasn't stopped him, as he's popped up in JLA issues, and is now soon coming back as a member of the Black Lantern Corps.
So, why is Doctor Light so unlikable when compared to mass murders like Sabertooth? I like Sabertooth. He's a ruthless villain, kills for sport (even children) and delights in the pain he causes. But I like him better as a villain because, really, killing is expected of certain villains. It's not that anyone endorses murder, but it's an expected result of the villain - and why the hero has to work to stop him. But rape - it simply makes thing too real, I suppose. It's a real crime, and it simply takes you out of that "epic struggle of good vs evil" and simply dirties the waters of the story.
I recall the ending of Kevin Smith's Spider-Man and Black Cat mini-series. It dealt with a rapist as the villain, and what was at the start a fun Spider-man story, was suddenly a cringe inducing tale. That mini-series failed on so many levels, not just because of it's chronically late scripts, but because the tone of the book suddenly changed.
I guess what I'm saying is that, even though we want our villains to be good foils for our heroes - there's a line even villains shouldn't cross. I really can't watch episodes of the Teen Titans cartoon, when Dr Light appears, and not remember what that character is really like. It's just creepy - and I wish Doctor Light would stop appearing in comics.