Mega Man X4 lets players complete the game as X or the Reploid Zero.
Mega Man X4 is the fourth entry in Capcom’s Mega Man X series and gives players a full campaign choice at the beginning: X or Zero. Both characters travel through the same broad stage structure, but their abilities, combat styles, and story scenes differ.
X fights primarily with the X-Buster, a long-range arm cannon that can be charged for stronger attacks. Zero is more melee-focused and wields the Z-Saber. Instead of collecting the defeated bosses’ weapons in the same way X does, Zero learns special techniques, including movement and combat skills that use no ammunition.
This was an important change from Mega Man X3. Zero had been playable there only in a limited backup role, whereas X4 made him fully playable from start to finish. Players cannot switch between the two heroes during a campaign, so choosing one creates a distinct version of the adventure. Sigma and Vile are major figures in the series, while Axl joins the central playable lineup later.