From Bulbapedia, the community-driven Pokémon encyclopedia.
Colosseum Master Kruger (Japanese: コロシアムマスター ルトガー Colosseum Master Rutger) is the ninth Colosseum leader in Pokémon Battle Revolution, and the third and final Colosseum Master. He is the head of Courtyard Colosseum. He has black hair, white skin, and green eyes. Kruger wears a grey suit with a rose in the lapel, a white tie, and two gold rings with a precious stone set in each.
(His Rose Corsage can be won in this Colosseum)
Kruger also seems to be the only Colosseum Master based on one of the designs the player can be (the Muscle Man's design, excluding clothes), complete with the Muscle Man's Sports Tape; despite having the Muscle Man's Face, he is a "Colosseum Master", rather than a Colosseum Leader.
After the player beats Pokémon Battle Revolution, Courtyard Colosseum turns into a 100-Trainer challenge. Kruger is the 100th and final opponent; he also appears every ten battles other than his final appearance. Every time he appears the number of Pokémon each Trainer has increases by one, until each Trainer has four Pokémon.