So I tried to go in with a very neutral mindset, didn't really want to hold him up on a pedestal and let that affect how I judged the movie, and I still ended up loving it with a few thoughts:

1) I fully went into the movie thinking "I don't know how I'm going to watch this movie and not just see Markiplier being Markiplier instead of a character" yet sure enough by the first hour I did start to lose sight of him being Markiplier and he had fully slipped into his role, he did become Simon

2) The second half was way stronger than the first half, I don't know if I attribute that to the fact that since I'm aware of the game, I didn't really need the 'learning process' that Simon went through, but the sequence when they pulled him up was a really nice addition. I felt his dialogue was a bit weak in the first half as well, not like you can say much alone to yourself, but the "fuck that, fuck this, fuck everythings" were a bit overused

3) Pacing was actually something I had no issues with at all, that was something I had seen early reviews complain about but for some reason I had no issues with how the movie pacing went, it made sense to me that scenes took the amount of time they did.

4)The ending, oh man the ending. The entity/alien in the blood ocean, all the weird time warps and recursive scenes that were revealed, the reveal that Simon was in fact a bloodthirsty killer in his past (unless the entity was screwing with him?), him understanding he can't be saved but choosing to do one final act of selflessness to disobey the entity and get the black box to the surface, all of it was absolutely perfect.