I'll preface this by saying anything I don't mention below, I liked.
To keep things short and to the point, here's a list of the things I didn't enjoy.
-Inconsistency in weapon details, some weapons were bear bones and others detailed.
-Protagonist design felt very lazy and uninspired, it's just a grunt with a weird face and a hat.
-There were a few time gaps where enemies could've attacked or shot the protagonist but just stood there doing nothing.
-The backgrounds were really bland and lacked environmental detail/variety. A lot of them were either just a grey room with stairs or a grey room with a ladder, usually only having the token pipes and stains.
-The gore wasn't very detailed and was pretty typical madness looking (I.e. hollow and bland looking.)
-The combat at times wasn't very entertaining, but I'd say about 90% it was fun to watch. Not much of a fowl there.
-Soundtrack wasn't anything special, very typical re-used sounds, samples and BPM. Was very empty sounding and lacking, which is unfortunate because I know for a fact that the composer can make truly great music if he takes his time and does his best. Felt lazy.
-When the wall explodes there's no debris or particles, just a big flame effect and a hole suddenly. Also why are they blowing holes into their own building on purpose?
-The center point, being the madhat and an undying/regenerating protagonist, is a unique and interesting idea. Unfortunately there was a lot of wasted potential. Like you could've had him do risky attacks, like running into an enemy sword/spear on purpose since he cant die to take him out. It's unfortunate because there could've been so much more than just generic gun and melee combat.
That being said, overall I still enjoyed watching it and for what it's worth I wasn't very bored watching. The idea's neat and fun, though an invincible protagonist kind of removes any tension the movie could've had.
Superb animation from the both of you as always. I look forward to your next release, hopefully you'll learn from this and make something truly jaw dropping. I believe in you!