Although killing Stuffy has been functional for a long time, it wasn't always pretty. We've recently been working to change that by adding new overlay effects, better code, and various effects (like a camera shake).
Killing Stuffy should be satisfying! I mean... errr, it should look good.
We're only ready to show the core lethal types, which include Electric, Fire, Frost, and Plasma. Other lethals shown in the scene are still in development (using placeholder visuals), but are not promised to launch with the final game.
It should also be known that the final behavior may change. For instance, Frost may damage you over time rather than an instant freeze.
There's still some minor work to be done, like bug fixes and improving the way Stuffy despawns. It can be quite tricky!