Great 1st act, great 2nd act, one of the worst 3rd acts ever
The first act is remarkably well done with it's stylized visuals and engaging plot. You are immediately put in the action.
Then, the the main character gets on the Skizm show. Cool stuff. Chases are well done. Humor is good.
Unfortunately, this movie because a cliche factory when the third act starts. The whole "team up and take down" plot is stupid and overdone. It's never even explained how they did it off camera as clearly Skizm would have been monitoring both contestants for the live view and would have heard their "plan".
A much better plot would have been for them to say "Hey kid, you made us a bunch of viewers and made us a bunch of money. No one thought you'd survive more than an hour so we're offering you a job at the company". This would have been consistent with his development as a character, mirroring his involvement with an unscrupulous kid's game previously. It would also eliminate the problematic scenes in the warehouse where Nix takes out like dozens of guards by herself that were far too over the top.
Or they could have had Nix wrestle morally with what she's doing after seeing how he was basically fish in a barrel and refuse to play the game.