Could use some more work
This isn't one of the best flashes I've ever seen. You might want to work on making the character move and behave more realistic, I think it to be a little ''stiff''. For the design and sound effects I don't have a lot to say about, but you might want to improve your drawing skills in combination with your animation skills, for example, practice some with drawing and animating blood, and making flames more realistic.
However, for a first video, this is not bad!