The music was pretty nice, and I like the character and his design, he seemed badass enough, but also raggedy and freaked out. The concept was really not original and seeing the same Dedmos series setting over and over is pretty boring. The monster was also pretty unoriginal, but at least you gave it some colors to mix things up, even though the colorfulness doesn't really fit the gray theme. The little bit of action with the zombie guys was good, and I liked the fight choreography and camera movements. That shot when we see his hand from a first-person perspective was really cool. That style switch, though, was pointless. Don't get me wrong, I like alternate styles in madness, but there was just no point here. It ended the same way it began-suddenly. It didn't have a reason to be there, nor was it doing anything unique. The animation on it was pretty good, but you could have indicated better that he fell over when backing up. Maybe a close-up when it happened or a wider shot to see his body would have done the trick. I did like the splash of colors when the monster roared. That bit with "changing symbols" was classic madness 4th wall-breaking.
Overall, this was a mixed bag. It felt like it didn't know what it wanted to be. Did it wanna be an alternate style movie about a monster or an unoriginal classic thing. Now, here's what I think happened and you can tell me if I'm right. I think yo felt bad that this wasn't original enough, so you tried adding extra stuff, but as you got lazy, you went back to normal. And now you're constantly mentioning that it's not original because you feel bad and you wanna make up for it. That gives me hope. I see potential in you. You could have just left it the way it was, but you actually tried to do something about it. You didn't fully commit, but you tried. My advice is to try to stick to one style, unless you can make the switch feel normal and organic or establish the other style early on. You should put in effort and flesh your more original ideas out fully instead of mixing and matching. You've certainly got the animation skills, and from your description I'm guessing you're young, so you've got a lot of time for improvement (though, really, you'll likely be improving your whole life)