Gary Oldman Craps On 'Harry Potter' Role, Says He'd Do It Differently Now

Gary Oldman is considered one of the greatest living actors alive today -- but if you take his own review of his work, it's all pretty trash ... especially as it pertains to 'Harry Potter.'

The Academy Award-winning thespian -- who's range knows no limits -- recently got candid on the 'Happy Sad Confused' podcast over how he feels about some the roles he's taken over the years, including Sirius Black in the 'HP' film series.

He played Black for a total of 4 films ... but as he looks back now, GO says he thinks his acting was actually "mediocre" -- and when the host scoffed, Gary freaking doubled down!

The reasoning behind this apparently lies in the fact that he didn't know his character was going to be killed off. As Gare explains here, he didn't read ahead in the books -- the way the late Alan Rickman did -- and says he would've played Black differently if he'd known.

Still, he goes on to say that he often criticizes his past roles -- and while a lot of people try and give him praise ... Gary apparently doesn't get all the hype. Indeed, very harsh.