Gohan is the son of Goku. Gohan is pretty much the most powerful. His power ignites when he gets angry,he doesnt learn to control his power till he gets older.Gohan fisrt showed his true power when Raditz was fighting and beating on Goku. Gohan explodes out of the space pod and headbutts Raditz with a power level well over 700 (which was not to far from Goku and Piccolo at the time), but the problem is that after he shows his power and goes back to his normal self he forgets everything that happens and just sits there. So as a child he is trained by Piccolo who is his mentor to control this great power that he has.Gohan plays some key roles throughout dragonballZ.For example when cell comes he goes super saiyan in the room of spirit and time but has more potential then that. So when he comes face to face with Cell, Cell pisses him off and Gohan burst into Super Saiyan 2 which is what Goku wanted to do orgianlly.At that point he was the stongest in the world. More to come....
