Robert Ryan did not receive an Oscar nomination for portraying Joe Parkson in Act of Violence.
Robert Ryan plays the other pow who is trying to track down Frank clearly to kill him. At first we know nothing about Joe other than he is a man with a limp and he clearly has a great determination in him. Ryan was the perfect choice for this role particularly for these early scenes and his knack for playing villains. Ryan with ease conveys a menace in him and is the dark specter Joe should be who haunts Frank. There is a strength just in his determined yet pained face. It is not something you might expect from a killer, he is haunted but his dark purpose is just as clear. This is not one of Ryan's usual heavy roles though and there is an honest strong motivation to the man's hate for the "war hero".
The truth behind Joe's hate is that Frank betrayed all of the other men in the prisoner of war camp including Joe which ended up with all of them being killed and Joe being injured. Ryan is very good in the scene where he reveals this to Frank's wife because it is less of revelation and more of allowing us to understand what haunts the man. Ryan has a strong intensity here and establishes that his intention is almost something more than personal for him but is rather a justice for all of the men whose deaths were caused by Frank. Ryan is very good because although he never seems to be the "good guy" in the film he very much shows the moral outrage that Joe feels from the situation.
This is a fairly short performance and one that is very much to the point, but it is a well handled. Ryan is very good in being almost just a ghost in a film one that both haunts and is haunted. I would say the biggest weakness not with Ryan's performance but with the character is the sub plot involving Joe's own romantic interest who tries to pull him from his vendetta. I just think it all would have been more powerful if it was clear that Joe was all alone and his revenge was all he had left in life after his tragic past. Nevertheless Ryan's performance strikes up the right balance between the hate Joe intends to inflict and the pain he feels from the past so that the last minute change in Joe is both believable and is rather moving. Although I do think the character could have been even better Ryan does do the best he can with the material he has.