A person who kills a prominent figure, typically for political or ideological reasons.
The assassin targeted the president.
There are quite a few assassins who have left their mark on history.
刺客 is a more literary or historical term for an assassin, often used in period dramas or novels, whereas 暗殺者 is the standard modern word.
Compound of 暗殺 (assassination) + 者 (person). The word 暗殺 is itself a compound of 暗 (dark, hidden) and 殺 (kill), reflecting the covert nature of the act.