The red Mega Man represents Zero, a Reploid with a red-and-white color scheme who appears as the Assist Trophy enemy.
The stage and music track represents Central Highway, the opening stage of Zero's debut game, Mega Man X where Zero is turned against X.
The first battle condition references the power of Zero's arm cannon, the Zero Buster, which is much stronger than X's arm cannon.
Other trivia:
In World of Light, the Zero (Zero Buster) spirit is featured on Dharkon's side on The Final Battle map while the X spirit is featured across from him on Galeem's side, referencing their occasional rivalry and origins, with Zero serving as the successor of Bass created by the villainous Dr. Wily.
