Gohan always had the potential to the be the most powerful warrior in the universe. He always held a certain “potential” inside, if released and controlled correctly could be devastating to any opponent. We witnessed that “power” when he became the first Saiyan to go Super Saiyan 2 and defeat Perfect Cell. Here’s a scene where Frieza (in transformation 2) taunts Gohan and thinks there will be no consequence for his actions. Boy is he wrong.