Raijin

and his brother Fūjin are the Legendary Stupid Brothers.

Background
The two brothers originated from an unknown village. They once killed their comrades over a meal, and calmed down immediately afterwards. After the incident, they were locked up in Konoha Strict Correctional Facility.

Personality
Raijin and his brother's thoughts revolve completely around food, and the guards of the prison would use this to their advantage, by controlling the food supply to keep the brothers in check. Both live up to their monikers as being very unintelligent, and they were scared into submission by Tsunade's strength.

Abilities
Both brothers have tremendous strength, being compared to the raw might of Tsunade's. In reality, even the prison they reside in is incapable of containing them, as they can easily break down the cell door. However, for all their strength, they are unintelligent and can be easily duped.

Mizuki Strikes Back Arc
While in prison, the brothers were befriended by Mizuki, who convinced them to help him escape by offering them food. Once they escaped, they fought Naruto and the members of Team 10. They were unable to beat the brothers, and it was not until Tsunade arrived and threatened to not give them any more food that they returned to jail.

Trivia

 * Raijin shares the same name with the Shintō god of thunder.