Uub

Since he was originally goku's pupil, uub was second to goten.

Going super saiyan!
In the past, super buu had absorbed gotenks and gohan. Due to being the reincarnation of majin buu, uub had some dna of gohan and gotenks. Due to this, uub could achieve the super saiyan transformation.

In the diablo saga!
After sensing goten in danger, and bulla as well, uub departed from the world tournament to the lookout. After discovering he could not transform, uub freed his friends out of their icy prisons with flame breath. While uub helped to fight diablo the ancient super namek, it was not enough. Uub attempted the evil containment wave, but diablo dodged this one, and bulla was hit. However, uub had learned from piccolo, and immediately freed bulla before she could not escape. After that, uub is among the justice fighters to be injured badly. Goten ultimately finishes off diablo. After being separated from majin buu by elder kai, majuub becomes uub's transformation after super saiyan, known as super uub/speed uub.