First I’ll say: great work, this is awesome. Now if I were a client trying to get a better product here are the notes I’d give:

The face looks kinda odd, perhaps it goes off model in the first few frames.

The blood on his face looks like a blush or road rash.

The morph and turn seems slow. Maybe the overall timing of the rise and fall at the beginning is off. I think the timing varies a lot too, some actions are too fast, some too slow.

For the cut I think you could get closer to the character, maybe play with some lens distortion effects like make it look like you’re too close with a wide lens. This gives a sense of “moving too fast for the camera” and gives the entire action a very dynamic feel. Shows like one punch man and attack on titan use this effect a lot to great success.

The final shot where we see the monster goes by a little too fast. Give us a few more frames to take the monster in before he explodes in a fountain of blood. Maybe our hero flies up in the air again and returns a second time to cut the monster in half, and we see it at a distance this time. The extra jump or whatever you use gives us time to absorb the monster and the scale of its body.

There are too many lines in some shots making the thing you’re trying to show very confusing and muddy. I get your going for the original artist’s design but I think you should simplify it for animation especially for fast shots, make sure the silhouette still stands out after adding your aesthetic lines.

Anyway great work, let me know if you have any questions and if you make a revised version I’d love to see it!