I mean, for me, its gotta be Freddys revamp.
It's a toss up between the Freddy and Doctor reworks. Probably Freddy though. I used to HATE facing him, but don't mind him at all now. I never played the doctor because he was boring and felt off but now I love playing as him.
to me, although the current Freddy is strong, his powers feel boring and requires less skill than the old version. His add-ons are kinda boring too. But I do think it is a good change.