Dragonball Z

[theeboredone]

I think with the Spirit Bomb, you needed a pure heart, but it was never mentioned about Kaio-Ken. Just that it put a huge strain on your body. However, given that Goku went up to x20, I'm sure those three could have handled x5 at least.

And I didn't read the manga, but in the anime, he was already in a fighter's stance before they grabbed him.

 

[Fuelbi]

iirc Spirit Bomb (prefer Genki Dama imo) needs a pure heart (either pure evil or pure good) to be able to use it. It's supported by the fact that SSJ Goku wasn't able to use it because he had rage in his heart (and instead absorbed it and became a badass). Though I wonder why Gohan never learned it. It was shown he was able to at least deflect it and he seems to be as pure as his father.

Perhaps because he didn't like fighting though