@ carver9: Yeah, and that was fat Janemba that got beat so easily by SSJ3 Goku. Goku said "Whoa, we were right to cancel the fight. This guy could destroy the entire universe! I've never felt a power like this before!".
@ vansonbee: I already explained it, Janemba only exists in the anime, so we use anime-canon to determine aspects of him. SSJ3 Goku was the strongest unfused character in the anime, so since Gohan fought on par with Buutenks for a while, Goku is stronger than Buutenks and maybe even Buuhan. This is because Goku said that kid Buu was gaining power instead of losing it, as he turned from Buuhan to kid Buu, meaning Kid Buu is the strongest Buu. Then, Goku said if he tried to at the start of the fight, he could have killed kid Buu at once. That makes SSJ3 Goku stronger than Buuhan in the manga, even though Gohan and Gotenks were both stronger than Goku in the manga. So, Janemba can easily beat ALL of the Buu's, including Buuhan and kid Buu.