If there is any character in Dragon Ball who can “beat” Goku, it is Grandpa Gohan. Grandpa Gohan is a kind and loving person who adopted Goku when he found him in the forest. Goku's personality and morality also come from this adoptive grandfather.
Grandpa Gohan is one of the characters in the series that doesn't appear much but is still loved by many fans. That has been clearly shown in the latest fan conversation created on the internet.
Many fans even think that Bandai Namco should add Grandpa Gohan to Dragon Ball: Sparking Zero (the sequel to the beloved Dragon Ball Z: Budokai Tenkaichi 3), otherwise fans will definitely be disappointed. Because clearly without Grandpa Gohan, Goku could have become a psychotic murderer wandering the earth until all life disappeared.
Originally, Goku was brought to Earth with the mission of destroying all humanity and selling the planet in a short period of time. Unfortunately, upon arriving on Earth, Goku fell into a ravine and hit his head, causing him to lose his memory. Thanks to that, he forgot the ferocious nature of the Saiyans and was raised by Mr. Gohan and passed on martial arts knowledge. Later, Goku became a new person with a kind heart, determined to become a warrior to protect the Earth.
In a viral Reddit thread, a fan named PerfectDecayRM brought up Goku's adoptive grandfather and said that the game would fail if he wasn't in Bandai Namco's game.
Sparking Zero had a lot of spots to fill on the list. But unlike many characters like Frieza, Cell, Vegeta… who took up multiple spots due to their transformation abilities, only one spot was needed for Grandpa Gohan.
Since Grandpa Gohan is a playable character in both Budokai Tenkaichi 2 and Budokai Tenkaichi 3 (two classic action-adventure games based on the popular Dragon Ball Z manga series), it's very possible that he'll actually make an appearance in Dragon Ball: Sparking Zero as fans have been hoping for.