If Buu trains, that would blow my mind. Regeneration is good, but it can't save you when you're going up against someone over twenty times your strength. Gohan stomps.
SSJ Future Trunks (Trunks Saga) vs Fifth (Second?) Form Cooler.
Hmm it'd be a good fight that's for true. Both are skilled but Goku would take it in that department but Piccolo's clearly the smarter fighter, he has regeneration but it takes time and some ki to do so. It could go either way but I'll give this to Goku 6/10/
Initial Meta Cooler vs. Imperfect Cell (Ginger Town)
I give it to Hirudegarn. I put Initial Hirudegarn on Buutenks level and Evolved Hirudegarn a bit above Gohan Buu. Meanwhile the 2 halves of Hirudegarn I put around Base Super Buu level so Gotenks would get stomped LITERALLY imo.