Or in the middle, and or you have your own opinion on him?
I didn't rrly agree with his principal's, but in the context of the show I liked him best and was rooting for him.
I saw him as the good guy honestly. Perhaps not toward the end, but in the beginning he was doing what he thought was a service to society. Whether that was morally right or not is up for debate though. Plus, it's freaking brilliant how long him and L's game of cat and mouse went.
He was a bad guy. I think he had like 2 or 3 episodes where he was doing hard justice and seemed like he had noble causes. As soon as Ryuk shows up though, he reveals that he's doing this so he can become the God of a new world and not just because he's trying to make the world a better place. He then goes on a rampage of murdering cops, grieving widows, and sending his father to his grave just to get what he wants.
He's a bad guy. He's my favorite character but he's definitely a bad guy. Saying he's a good guy is like... like in Godfather 2 where Tom helps out the senator who passes out at a whore house and wakes up in bed with a dead prostitute. Tom helping the Senator is like Light helping society. It's a bit cold but it's doing some good to someone. Even then it's iffy, but let's call it a nice act. However, you can't call it nice when Tom set up the whole situation and was responsible for the whore getting killed and did this solely so that he could have the senator in his pocket. Much like how Light is killing undeniable good guys and innocent people just so he can become the god of a new world. Light is doing like one nice act surrounded by a ton of bad ones all for the purpose of achieving a nefarious goal. Nothing "good guy" about it when you take it all in as a whole. Neither his actions nor motivations were particularly good.
Definitely a villain. The end goal he has for his so called ideal world involves taking the lives of criminals who may have only been involved in minor crimes and killing off those who threaten his authority as he gained a serious case of God complex from gaining the Death Note's power. Any redeemable justifications he might have had for use of it when he first gained its power went down the toilet as he let use of its power get to his head.