In his defense (minor defense), Erik is at least aware that he's a complete scumbag.
Depending on how one looks at sin shades how evil we see characters, IMO. Adam and Eve were cast our of Eden because, once they gained knowledge of good and evil, they had to choose between them. Ignorance is sinless.
In that regard, I'd say the Red Skull is the most evil. He knows what he does is wrong, he goes to great length to be extra sadistic and his genius (operating a crime syndicate isn't for dummies) could easily enable him to live a better life, if he so chose. But all he does is go around kicking puppies into orbit.
Compared to him, Sabretooth and Bullseye are just kids with impulse control problems