It's looking much better.
Great progression.
The new key helps a lot.
The animation you have is very physical, and fun.
I would suggest you keep it as primarily a slam attack, as if he is making contact with a surface.
You could still have stuff pop up or a wave shoot out or something.
But If the player gets under his fists they should definitely take physical damage.
If you're going to make him shoot special stuff I would say make it completely different than the slam:

From a gameplay perspective it will allow the player to pick up instantaneous visual cues about whats going on.
This will allow them to react more quickly.
Sound and color is also a good way to alert the player of a specific action.
Then throw in a move that tricks people.
"Oh hes gonna sma..... oh no! he did the other thing!"
I just realized that I didn't even explain the bounce in terms of animation theory.
This is whats called "Resolve".
It can take on many forms and is used in general to dissipate energy.
In this case we are trying to "resolve" a fast motion and an impact.
Effectively we are trying to show weight.
To simplify, basically weight bends stuff at joints or "pivot points".
Try doing this attack in front of a mirror.
But hit a pillow or something so you don't hurt yourself.
This is known as "Acting for animation".
The most resolve will come from your upper body, head, and shoulders.
They will bounce a lot as you naturally stabilize your weight.
The primary pivots will be your fists.
They will not move much.
The Secondary pivots will be your elbows.
They will bend some but will also act as a pivot to your upper body.
Something like this:

The main reason why he appears "jelloish" is because you are implying a pivot by stretching from here:

Where as a more natural pivot is the elbows (and/or hands):

Where you place a pivot isn't really right or wrong.
It doesn't matter so much if there should be one there or not.
Depending on the character and the action unrealistic pivot points can work really well.
Also keep in mind that no matter what you see in the mirror, you will want to exaggerate.
There a bunch of different ways to use resolve.
This bouncing type of resolve about fixed pivots implies that he is making contact with a surface and stabilizing his weight.
If he were not hitting something, or something very light, you would still use resolve but in a different way.
Take for example a golf club.
Hitting the ground and hitting a golf ball.
In both there is anticipation.
In both there is action.
In both there is impact.
In both energy dissipates.
In both weight stabilizes.
In both there is resolve.
But they feel and look different.
I completely glazed over this topic last time, so sorry for that.
Another cool trick I've used here is the "Shrink Frame".
Just before he shoots I shrink down his upper body.
Then on the next frame I make it larger:

You can use this trick in lots of situations.
When you find a good spot for a shrink, try sizing it down more than you would think possible.
It's often surprising how exaggerated this can be and still work really well.