Light started off decently enough, but by the time he started slaughtering cops and vowing to exterminate all lazy people in addition to criminals, I'd say he's definitely a villain. He's not even portrayed in a sympathetic light like, say, most of the GTA Protagonists or something.
Haven't read comics lately, so I'll just stay out of it on Venom.
What about someone like Galactus? He's listed on some Greatest Villain lists and was specifically created as a Super Villain...but also as a God entity that is beyond the human concepts of Good and Evil and "a living force of nature". Not that I actually want to nominate him, it just seemed an interesting question.
--
In this world which will someday fall to ruin...
...dreams and hopes don't matter at all.