Continuity mistake: When Viktor captures Raffa, he puts a zip tie on his wrists. The excess zip tie parts hang off to Raffa's left. But as Viktor is putting him in the car, the excess is on Raffa's right. (00:45:25)
Revealing mistake: When young Viktor does his first two kills, he is using a revolver. I think a 38 Special by the looks of it. As he shoots, there is no kick to the gun. (00:23:25)
Revealing mistake: Right in the beginning of the movie, we see young Viktor holding a gun to a young girl, about to shoot her. The gun is a revolver and as it comes into focus, you can see there are no bullets in the gun. This is part of a later scene in the movie where Viktor kills his first two people. As he's shooting, you can again see there are no bullets in the gun. (00:01:20 - 00:23:10)
Continuity mistake: Older Viktor's ears are noticeably different from one another. Like one of them is deformed or something. Not as result of injury, but by birth. Young Viktor's ears are normal.