Vegeta killed Yamcha once, and Buu killed him a second time.

Technically it wasn’t even Vegeta, it was just the little green men that Vegeta and Nappa had seeds for.

Krillian was actually alive to see that death.

As for the death by Buu, that was being turned to chocolate and then being eaten.

Krillian still has him beat on number of deaths, picking up an extra death on planet Namak.