When the time came, he was still too weak to do much damage and proved he wasn�t ready for battle when he disobeyed Piccolo�s orders to attack Nappa. Young Gohan eventually led to the defeat of Vegeta when he reflected a spiritbomb given to Krillin by Goku who missed.
To wish back those who had died in the battle, Gohan and friends set off to Namek to gather the dragonballs. On arrival they realized that they weren�t the only ones there. Vegeta and Freeza were there as well. As time passed Vegeta sided with Gohan to make sure that Freeza didn�t get the dragonballs before he did. Eventually Gohan and Freeza met on the battlefield but Gohan didn�t stand a chance against the Lord of Evil but he had his moments.
Gohan, while training in the room of time and space, he becomes the fourth to reach super saiyan while getting the training of his life by his father, Goku.
In the Cell games, Gohan turned out to be quite the warrior. He was the first saiyan to turn SSJ2. At that level he was way stronger than anyone else and might have defeated Cell but Vegeta foolishly tried to attack Cell. Cell, fully aware of his attack, shot a beam of energy at him that Gohan blocked. In doing so he lost the use of his left arm but still fought when he had an image of his father.
Later he entered a tournament as a "Great Saiyanman" where he disguised his name so that one of his high school buds wouldn't know his true identity. He also married his high school sweetheart Videl and had a daughter named Pan.
Eventually he was trained by a god named Kaioshin and received the zet sword that he pulled out of a stone and raised his power immensely clearly making him one of the most powerful saiyans.
