Mercenary

A mercenary is someone who takes part in an armed conflict for the purpose of personal gain, usually financial. They are usually working outside of the involved governments and typically do not care about the politics involved.

History
Cable was a mercenary who worked for a colonel. They fought to bring democracy to Genosha, but when the colonel took over he called himself Leader and failed to bring about his promises. Cable took exception to this and began attacking Leader's forces.

Klaw employed mercenaries in attacking Wakanda, but they were defeated by T'Challa.

In the Comics
Deadpool and Silver Sable are mercenaries.