South Supreme Kai is one of the ancient Supreme Kais from the era when there were four instead of just one. He was easily the most impressive of the fallen Supreme Kais for obvious reasons.

Despite Kid Buu being stronger than Goku in Super Saiyan 3, South Supreme Kai managed to make a fool out of him at times. The little pink monster never truly held the upper hand against him.

And South Supreme Kai does not take him seriously enough, even tossing his severed hand as a mockery.

He had no idea that Buu could absorb others with his strange gum-like body, and he becomes the first victim to be absorbed. It was almost an honor, because it showed that Kid Buu was afraid of losing.

And then he becomes part of a modified version of Buu. I like to believe South Supreme Kai was the foundation for Super Buu, though this original form looked like an even more muscular version of him.