The hitboxes are a bit too large, and the last level was just unfair...
I thought the last one was kinda funny, but the way it just forces you to die without a chance for you to react was kinda unfair. I would have a wall push you instead of a spike killing you.
Something that could help would be a small freezeframe after you die, after you die, you can't control the player for a few frames to give the player a chance to fix themselves.