This isn't bad for your first animation (on this site at least), and I like the creativity behind the abilities of the various stick figures you've created. However, there are a few things you should work on. For one, this absolutely needs sound effects. You'd be surprised at how much adding a punch sound can increase the perceived power of the impact on the various hits. I also don't really like how the music just plays over top the whole time, maybe if you cut it out during the sections where the bracket is shown it would be better. Another problem is that all the action happens in a small white rectangle with no surroundings or scenery, where the edges are finite. Try creating a larger room for the stick figures to fight in, with platforms and whatnot, and then move the camera to where the action is.
I'm not an animator, so I can't tell you how to do all this. You're going to have to figure it out on your own through a lot of trial and error. You do have one amazing resource in the tutorials animator Hyun has created, and I highly recommend looking him up on Youtube and learning everything you can from him. This is a good start; if you stick with it you could really make something amazing.