General Ketheric Thorm is one of my favorite characters and is very underrated in my opinion.
His first scene was fantastic and in all of Act II you feel him as fearsome as he is.
Besides that, I like the fact that is (the only?) character of BG3 who is driven by deep love and for that willingly becomes a villian. I think he is acting really relatable and realistic.
And man, what a moment it was when he became the Avatar of Myrkul.
I wished the was a way to really save him.
Orin and Gortash may be cool (and Orin is as hot as it gets) but a too edgy, crazy and over the top.
I value Gortash over Orin though.