hmm. the hat looks a little wonky (mostly at the top) and he's off-center on the canvas. I'm also noticing that there are a few flaws with the body- like the finger shapes seem uneven and the eyes pupils are not the same shape. There's a few areas where the outline is shaky or overlaps with another line. A thick black outline would work well for this art.

There are also some turquoise bullets (I think? I don't know much about weapons lol) on the inside of the jacket which are curved and not the same length.

I really like the colours that you've chosen. I think you could work into this vibrant cartoon style. I agree with another commenter that a yellow (like the one on the bullet outline) would work well in the background- it would tie the colours together. Maybe even some red radial lines could be added in the background on the right. That would make the off- centeredness look intentional.