opportunist
n. countablen. someone who takes advantage of a situation to get what they want, even if it is not fair. They often act quickly when they see a chance to gain power or money.
n. a person who takes advantage of circumstances as they arise, especially to further their own interests. Often carries a negative connotation of exploiting others or situations for personal gain.
He is a political opportunist who changes his views to win votes.
The company acted as an opportunist, buying up failing competitors during the economic downturn to expand its market share.
While some viewed the CEO as a visionary, others dismissed him as a mere opportunist who only entered the industry when the market was at its peak.
From French opportuniste, equivalent to opportune + -ist.