Well, Negan first appears in the series as a major antagonist. He has a very distinct personality. He's confident, often to the point of being cocky. His group, the Saviors, would extort other communities for resources. He uses fear as a tool to control those around him. His actions have a huge impact on the other characters in the show, like Rick and his group.
Well, it depends on your perspective. But generally, Negan is considered bad in the comic because of his cruel and violent actions towards the main characters.
In the comics, Negan is a morally ambiguous figure. He's done a lot of bad things, but there are times when his actions might be seen as necessary for survival in that world. So, it's hard to give a straightforward answer about whether he's good or not.