well. it depends. in the books, both the old EU non-canon books, and the new ones that ARE canon, thrawn is very much portrayed as not really evil at all. just an efficient general that allied with the empire because the rebel alliance didn't have the strength to defend the chiss from their enemies. (thrawn's species is the chiss, they are notoriously isolationistic so VERY few of them have left the chiss ascendency or let anyone within their territory) rebels thrawn has a lot more cartoony mustache twirly villain moments, but still comes across as much less of a villain and much more of just an antagonist by circumstance.
the empire is notoriously racist and almost exclusively employ humans, so for thrawn to not only IN the empire, but to be one of the highest ranking military officers should tell you what you need to know about him when it comes to being a bad guy. but, like others have said, he's an atypical villain in that he's not interested in vengeance, he's not interested in body counts. he wants to reduce the cost of life, not only on the side of the empire, but the side of his enemies as well.
it's kind of interesting to see this version of him though. he's definitely lost something, but i think that's because he's been stranded and lost A LOT of men. even if those night troopers are under his command, i don't think he thinks of them the same as regular troopers since they are most likely dead and brought back as revenants of some kind, a la marrok. for a guy who wants to preserve life at all costs, looking at a bunch of walking corpses dressed as your troopers probably does a number on him.
and like i said, he's not interested in vengeance at all, and yet he still sends people after ezra. he keeps intel on where ezra is, showing that he's still paying attention to a hermit who's likely just trying to be left alone. i imagine thrawn sent several cadre of troopers after him and none have returned, so he's stopped sending people after him, and yet he STILL keeps intel on his location on him. but then ultimately admits that the ONLY thing that matters is getting out of that galaxy.
i'm assuming that thrawn will pull some 4d chess on baylon and shin, resulting in baylon's death, maybe shin's as well but i think she'll survive the season and disappear for a while, only to join team ahsoka later down the road. i think that the witches will also end up going back to dathomir and repopulating the planet with night sisters/brothers, though i don't know where thrawn will be at this point. i really like the idea that he gets back, and looks to be remilitarizing the empire so team ahsoka go after him, but his death results in showing that he was holding back the first order, but now that he's gone, it galvanizes them into action.