He dies permanently but Goku thinks he isn't gone forever and will some day return.
He may possibly be Uub who Goku fights in the tournament.
He turns into Kid Buu.
Kid buu was created when vegeta and goku were in buu and remove all the absorbed characters including the overweight buu
Super Buu > Kid Buu -Kaioshin just said Kid Buu is just most DANGEROUS OF ALL BUU that not mean him is the strongest -Goku When Inside Buu him say him can't beat super buu if him go out him would be killed -Super Buu is more smart than Kid Buu -Piccolo even think SSJ Gotenks stronger than SSJ3 Goku who par with Kid Buu Ultimate Gohan > SSJ3 Gotenks >= Super Buu >>>>SSJ3 Goku = Kid Buu
kid buu by a long shot ss3 goku<kid buu while ss2(anyone)>cell
goku ssj4 is way stronger than kid buu because buu wouldn't defeat even a great ape which ssj4 would
Goku killed buu (buu in his final form as "kid buu") with the spirit bomb
SSJ4 Goku, of course!
Goku and Vegeta take Majin Buu (the fat one) out of super buu
He actually killed kid buu with the spirit bomb
Goku used a Spiritbomb on Kid Buu with all of the Earth's energy and Buu disintegrated but was reincarnated as Ubb
Buu never killed Gohan. On the other hand, I believe Goku killed kid Buu.
Vegito of corse as he was made up of the fusion of goku and vegeta and kid buu doesn't stand against goku's spirit bomb.