Bommer

Biography
Greiger is a physically well-built Duelist first seen in the Fortune Cup tournament, battling first against Leo (who was posing as Luna), then against Crow in a Turbo Duel, although he was trying to duel Yusei. He is from Central America, and he believes his village was used by Goodwin as the site of an "experiment" to summon the Crimson Dragon. The experiment completely destroyed the village, resulting in the disappearance of Greiger's younger brother and sister. Greiger is enraged to learn the truth prior to his match with Yusei, and he attempts to take revenge on Goodwin for his village's destruction.

Manga
In the manga, Greiger was once called "The Undefeated Giant" but he was defeated by Jack Atlas who mocked him for not being any challenge to him. Greiger enters the D1GP for a chance to get revenge on Jack. His first opponent was Yusei Fudo. Despite putting up a good fight, he lost to Yusei and blamed the loss on himself for being too focused on his revenge on Jack.