One of my favourite so far! This is really well made! The ragdoll physics after getting hit is hilarious, I don't think I've seen anything like it in a game like this. The game also looks insane, and the commitment to pixel-perfect visuals didn't go unnoticed (I really hope you used a shader for that, since some of those animations must have been nightmarish otherwise).
It was definitely a bit on the harder side though, it's already been mentioned, but some extra i-frames would be great. Also I feel like the batteries should either have fixed spawn locations, or choose from a list of spawn locations, since the fully random system was a bit unfair at times (there were batteries that spawned in walls and enemies).
And while the game's visuals were stellar overall, the first few areas were a bit bland. Still competently made, definitely not bad by any stretch of the imagination, but the game only really started to pop in the last few areas, and I'm a bit worried that a good chunk of people will quit due to the difficulty before seeing that.