Let me also say that Roberto has done a fantastic job not just on this forum but tons of forums he works on every day.
For the next challenge, I think desinegration could be still the general fx. there’s really no fx too small for a challenge, because we’re mimicing in some cases, and most others trying to make believable photo real fx. (that’s a run on sentence) I look at the 10 second club for inspiration, seems easy but you can do a lot with very strick guidlines. here’s a simple example, that can be very complex
gray sphere floating over a poly grid plane. Destroy/desinegrate the sphere.
level 1
shatter sphere, make rigid bodies, add gravity.
level 2
add particle debris, random small size, particle dust/smoke. Lighting and advanced rendering set up.
level 3
emit particle debris from cracks, set instanced rotations to fake correct movement (like rigid bodies)
level 4
fluid dust/smoke
level 5
skin outter shell burn/peels/flakes off (cloth sim)
level 6
objects on the ground burn, and disinegrate in to ash
level 7
starts to rain, remaining particles pool and puddle, water muddys and flows off leaving the grid clean.
there’s tons of alternates one could do with this. Plasma ball hits the shpere first, or it’s made completely out of lays of cloth and litterally turns to ash and floats away. So a beginner can do it by just doing level one and doing it well, and someone more advanced can push further to level 4 or 5.
this is pure fx, no time to set it up and lots and lots of fx work.