X-Caliber: [USA] Cybernetic mercenary from Valiant Heroes - 1.
X-O Manowar:
Xilonen: [Aztec Empire/Mexico] An Aztec goddess of maize.
Xocotl: [Aztec Empire/Mexico] The Aztec god of fire and the stars.
Xolotl: [Aztec Empire/Mexico] The Aztec god of lightning who guides the dead to the Mictlan.
Xolus Cor: [USA] Star Seed from Broadway Comics.