Xicor

Xicor is the best friend of Mercury. They often fight together and fuse. Xicor is the same age as Mercury, and they both are about at the same power level. While Mercury is stupid at sometimes, Xicor is serious at most of the times. He and Mercury fused when they fought against Mira in the Black Arc, and he also fought against Time Breaker Mercury, the winner was Xicor. Then when Mercury fought against Mira in the timenest, he went there to help him. After Mercury's sacrifice, he fought against Keita and he won.

Differences (Dragon Ball M and Dragon Ball M*)
DBM* didn't show much about Xicor yet, so this is uncomplete.