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. At some point in there past they had an encounter with Tsunade. The details are unknown but what ever it was the brothers have been terrified of her ever since.

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.

Abilities
Both brothers have monstrous strength and stamina, only increasing to higher levels as they get angrier. Also, with their power, they are able to jump great lengths and run at high speeds. Their strength has been said to be greater than that of Tsunade's. Consequently, the prison they reside in is incapable of containing them, as they can easily break down the cell door. When even Shikamaru, Ino, and Chōji held them in their Shadow Imitation Technique, Mind Body Disturbance Technique, and Partial Multi-Size Techniques, they were able to break out with brute strength alone. However, for all their strength, they are unintelligent and can be easily duped.

In addition to their brute strength, both brothers have shown be to impressively resistant to damage. They were able to easily take blows from each other, and Tsunade, without any sustainable injury.

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.