Klaus vs The Volturi vs Lord Voldemort
HANNIBAL, YES YES YES
But he is Spike because he drove rail spikes through people's skulls. He was pretty evil at some point. Funny, but evil.
But that is the thing you see.
Soul = Conscience. No Soul = No Conscience. He wants, he does. Concepts like Wrong or Right mean nothing. Every vampire is like that. However Spike, I'd say was one of the most human vampires ever.
When compared to Angel who is an outright monster and maniac, Spike never acted out of pure evil intent and most of stuff was either connected to his human self(even the torture with railroad spikes happened to the people who made fun of his poetry when he was human). He never did something for outright sake of evil. It was always Drusila, holding her attention, supporting her, not letting Angel take her. He was playing a role of villain to woo a girl. And even that Spike had certain sense of self-loathing of what he became.
Once Drusilla was out of the picture, Spike's more human qualities resurfaced.
But he never was someone who would be defined as vilain. He was Buffy's antagonist and Angel's FOIL, but thats it.