Motivated by private gain.
A person employed to fight in an armed conflict who is not a member of the state or military group for which they are fighting and whose primary motivation is private gain.
One hired to engage in a figurative battle, as a corporate takeover, a lawsuit, or a political campaign.
Mindful of, or promoting, only one's own interests.
That searches for a target automatically.
The selfish promotion of one's own interests.