Nice job! I didn't think the end boss was too difficult, though maybe a little annoying at times. I liked the artwork, especially the cutscenes with the boss, great touch! However, I do agree with the comment about the controls.
The jump feels floaty and odd, and the attacks aren't very satisfying and feel slow. If this were to be pushed further, those are the #1 things I'd like to see improved. The level probably doesn't need to be as vertical as it is right now. With a smaller and more responsive jump, you could focus more on fighting through the level horizontally. The boss is already on a mostly flat plane, so the huge jump isn't needed there either.
Anyway, I beat and enjoyed it! Your games have tons of potential, keep it up!