Ben Affleck has been one of my favorite actors since I first saw Dogma as a kid but many people I've talked to in real life and on r/movies seem to dislike him as an actor while praising his directing.
I think he's a killer director (hard to believe Gone Baby Gone was his feature-length debut) and a damn good actor, too.
Forget Gigli sucking, that wasn't his fault. When has he ever given a bad performance?