That’s a tough call. I’m tempted to say TPM Anakin but then I think about how Christensen is an older actor and should have done a better job. I mean, whose fault is it that Little Annie was such a lame character? Certainly not the kid, he was like nine years old or something …then again, can Christensen even be blamed? He’s not an inherently bad actor (I don’t think, I’m not sure) so blame would fall on the writers, directors and whoever cast him for that particular role.
The character was written and directed to be a whiny unlikeable jerk. If actor delivers such character, that means he did a good job.
I certainly think it means the actor did a good job. I think Lucas deserves 90+% of the blame for the acting/dialogue delivery/etc in the PT.