Diabel

Diabel is one of the few known beta testers among the players trapped in Sword Art Online and steps forward as the leader of the raid party formed to challenge the 1st Floor boss, Illfang the Kobold Lord. His tactical planning and rallying speech before the fight help the assembled players clear the boss with almost no casualties, setting the tone for how the front lines organize themselves for the rest of the game.

Publicly, Diabel presents himself as a strong, natural leader focused entirely on his group's success. Privately, he has a more self-interested streak: he quietly tries to secure an advantage over the boss for himself, including attempting to buy a weakened weapon from Kirito and maneuvering to be assigned the glory role in the fight rather than a purely supportive one.

He never gets the chance to see that ambition through, Diabel is killed during the boss battle, his death becoming the spark that first exposes tension between beta testers and the rest of the raid.