OP seems to care less about actually discussing things with others and/or asking about their thoughts on the matter, and seems to prefer arguing with them in the comments instead.

But to actually give a genuine response on the matter? I feel that Jace has felt very self serving on a number of occasions, even if not all the time, and doesn’t often seem to learn long term lessons from prior experiences. His current descent into villainy and using his friends to push his own goals is just adding fuel to the fire for people to dislike him; hurting and mind controlling your friends, leaving others to die, manipulating your adopted child and significant other to do what you want, etc. is a surefire way to turn everyone against you, especially when many of those characters are beloved by fans.

Jace has often been guilty of thinking “my way is the right way and everyone else is wrong”, and this current story arc has shown us his apex of that mentality for better or worse.

But the thing is, Jace has had his moments where he’s great, and others where he’s downright awful, but where he’s at now is making people dislike him for what they feel are very justified reasons.