Goten, 2nd son of Goku & ChiChi, may have been stronger than his brother Gohan. This is why, Gohan one day was explaining how to become a SSJ, that you have to train hard and get really really really mad to turn. Well right after he said that, Goten backed up and turned SSJ for the first time with no trouble, no anger or anything like that. Gohan was surprised. Goten was most likely the Strongest DBZ character, If he trained as hard as his Dad.