Tron

Tron was formerly involved with Dr. Faker's business, and has sworn to take revenge together with his followers III, IV and V. Usually he acts very childlike, enjoying cartoons and playing video games to the point where he bursts out in fits of laughter. However when he is talking to his followers, or announcing his plans to others, he is more mature, while always maintaining a smile on his face. He is later revealed to be a scientist by the name of Byron Arclight, who is also the father of III, IV, and V, all of whom have thrown away their family name for the sake of revenge. He, along with Tsukumo Kazuma, worked along side Dr. Faker to attempt to find the door that would lead to parallel worlds.

They were eventually betrayed by Faker on their journey, who sacrificed them to open the door, as two soul offerings was necessary. As Byron and Kazuma fell through the portal, Byron swore revenge against Faker. When Byron returned, his form was warped into that of a child and he took the name "Tron". (Source: Yu-Gi-Oh! Wikia)