Dragon Ball Forum

1. If Piccolo learnt how to use Kaioken would that make him possible the Strongest Person in DB verse?
 
2. Can Cell use Kaioken?

@Newten said:

Presumably Kaio-ken becomes unusable once a Saiyan achieves the Super Saiyan transformation, otherwise I don't see why Goku wouldn't have used it (the episode where he used "Super Kaio-ken" doesn't count, that was filler and therefore non-canon) so, since Cell is essentially like a Super Saiyan, I'm pretty sure he can't use it either. Piccolo on the other hand never really achieved a transformation (Krillin called him a Super Namekian once, but that was just because he was so powerful) so it might be possible he could have used it.

Would that make him the most powerful fighter though? I doubt it. You'd have to do the math and get all the official power levels to find out for sure though I guess.

And if you're comparing him to Vegito, no chance.

The reason goku doesn't use super kai-o-ken when he was alive because as Mister shin pointed out, It would kill him, but since he was dead already it wouldn't have hurt using it for a short burst punch against Pikkon.

@shonen:  
When Goku is dead, he retains his body in the afterlife. 
He can still get destroyed in the afterlife, however King Kai can reconstruct bodies, thats what he did for Chaiotsu.  
But you are correct. sensations like, pain, hunger etc. No longer apply when he his dead.  
Although Goku still likes to eat when dead :P