On one hand, he killed loads and loads of slavers, and helped to bring down their extremely brutal empire by aiding a slave rebellion. On the other hand, he also killed a bunch of people who probably didn't need to be, to the point that the mer describe as the leader of a Elven Pogrom, and he also killed a bunch of Khajiit who weren't even doing anything because he mistook them for elves.
He was also a gay insane cyborg from the future with a Mega-Man style arm cannon, and I'm not sure if his homocidal tendencies inspired from his Shezzar-Akatosh Duality Madness make him 100% responsible for his own actions.
I'm not sure it's really worth attempting to ascertain the morals of a being blessed/cursed with some form of divine-given bloodrage.
I'd also be careful considering the Song of Pelinal as pure canon as they're from the 2nd Era with the source being manuscripts which have not been dated. They may not be accurate at all and may be falsehoods or even propaganda.
He's got this cool as video about him though