Hi Dawk!
First, this is a cute character and your keyframes are very clear and powerful. They all convey the meaning and intent of the pose very well, and there's nothing to change there. Also, you reminded me of how enjoyable kirby minigames are, thank you.
As for the smear frames - yes, they aren't exactly working. There's a few parts to why
-The smears are noisy, and pixel noise break fluidity, interrupting the flow of reading the movement. I would recommend smearing with large blocks of color.
-The smears are not isolated to just whats moving the fastest. A smear is technically a stand in for a frame which does not exist - the frame between the frames is drawn with motion blur. Not blurring in the gaussian blur sense, but more a stretching of the object. For the punch for instance, I would isolate the smear just to his fist.
-You smear things that don't need it. The head turn for instance, that effort would be better spent on other areas than adding a smear to the nose. In the end it adds visual priority to something that doesn't need it. You could, instead, have the ears lag behind and catch up. I feel like that would not detract from the information and sell the movement as quick.
-The teleport (which is kinda a smear!) is used because he is moving too fast to see, if I'm reading it correctly? But then, the direction of the pixels go in both directions, away from where he will be moving. I would suggest a quick blink before the cut away, wherein he assumes a movement pose.
-For those smears when he is assuming a fighting stance, it would work better to draw the tweens for the arms and such on those frames. There is power in firmly and smoothly assuming a stance - rocketing between steps actually makes it seem less well trained!
For the blue lines radiating in, I think they work, but would work better if they held on him, retaining the energy for another frame or two before vanishing. The dissipation conveys that they are not really clinging to him
That punch will really benefit from secondary animation! The cloth, ears, everything. He was just moving faster than light, and hits something with that impact. They will be lagging behind at first, but then immediately he stops, fist transferring all that kinetic energy into the thing he's punching, and the ears and shirt will catch up to him in a moment and swing forward, before returning to their rest position. I think this is the crucial element missing from selling the impact.
Let me know if you'd like an edit! I recommend trying secondary motion first on the list, you'll be able to clearly see where its preferable to the smears.