Solid 3D platformer bones, and the models are very good!
My suggestions - when resetting to a checkpoint, at the very least cancel all momentum, since you're snapped back instantly and in whatever direction you're facing, you can just launch yourself off the edge of the map. Might not seem like a lot, and it really isn't, but it helps. And drop shadow to help figure out where you're landing while you're in the air.
The theme is a little weak, but that's not really a big deal, the important thing is making something, which you've done! Hope you can come back to iron things out and maybe add more content, would love to see other Justice mascot models! Thanks for submitting!