It feels quite solid! Characters, story, humor, and unique mechanics.
I didn't understand the radius of the release energy. It looks like sometimes it didn't take damage to nearby enemies even though they were inside the yellow explosion area.
I think you can add more challenge to the game and more speed. Sometimes you don't have enough rage to explode tough guys, and you need to shoot yourself for quite a long time to refill it. Consider making each shot more powerful, reducing the amount of bullets in pistols, and so on.
You can also start to add some juice to your game - VFX, camera shakes, etc. It could make it much more dynamic, even with this simple art.
Wish you good luck