Originally Posted by Katsunami
Then, you have stated why there are so few fantasy novels where the main protagonist is evil; he can do basically anything he wants, he is probably the most powerful character in the story, and is impossible to stop if you want him to win
No, previous post just explained why evil tends to be more powerful than good.
What you're positing presumes:
a) the evil character is omnipotent (they're not, it's just in an even playing field, evil has the advantage); just because you're evil doesn't automatically mean you're powerful
b) novels are also market-driven and editorially-driven; maybe editors don't want to read about evil characters, and readers want sympathetic characters.