Beast Gohan is the strongest form of Dragon Ball's deuteragonist Son Gohan. And it makes him the strongest Z-Fighter.

The original Super Saiyan form served as a base that several Saiyans built upon. However, after Goku witnessed Gohan's potential ... but his rage is pulled out during a fight against Vegeta ...

Gohan has surpassed his father, Goku, several times throughout Dragon Ball's history, as these examples illustrate.