Is Light a hero or villain?

Villian, he killed people like a boss!... by writing their names in a book and having middle management take care of the splash back(See L and the Police).

Depends of who you ask if someone like light were to exist... I wouldn't have any remorse for those he killed

i think he's a villian trying to be a hero, but killing in the name of good.

Light had good intentions about trying to purge the world of evil, but then the power went to his head and he started killing innocent people who got in his way, so I would say that he started off as an anti hero and then became a villain towards the end.

When Light forfeited the Death Note to Ryuk, his memories as Kira was removed. And when he helped L, there where like best friends. Sometimes I think that if Light had not regained his Kira memories once again, L and Rem would still be alive. Then we would not have seen Mello and Near. I suppose that Ryuk would have passed the Death Note unto someone else.

In the end, however, the Death Note corrupted Light Yagami's mind that it made him insane that he was willing to kill the one person(beside Misa) who actually cared about him: Kiyomi Takada(The news reporter who might have been his wife if the Death Note never appeared before him in the first place).

I think he's in the grey. He has a justification in his crimes. So I'd say necessary evil if it has to be villain or hero.