Letterboxd
The practical effects in this movie were really good. I think the last time I saw a film where I said "Damn" was Elysium in some scene where a mercenary gets his head blown off and it was just incredibly well done.
The character itself was a little all over the place. There is an odd almost out of place scene at the beginning where he thanks his mother, which does not even gel with the rest of the character. There is a romantic obsession that feels kind of forced, where for some reason his romantic infatuation sort of dominates over his revenge and his desire for stardom? He isn't a particularly likable person even before the transformation (which could have been fine), but the film seems to be trying to make him so which felt forced.
Some of the dialog was pretty weak.
Some of the side characters seemed to be maybe beyond their depth?
I think the biggest miss here was that they should have made him start as someone who we think is good, but that the audience gradually realizes was always a monster. So that the transformation only allowed him to be honest about his real nature. Instead, everything happens to him for most of the film. He walks through the world being obviously defrauded and cheated by those around him. It's like they wanted to provide a reason for his behavior, but they removed all agency (and sense) from his character and so made him a victim rather than a monster.