It's a common trope in movies that certain people, either spies or mercenaries, specialize in assassination. (An apparently well-paying but wearing specialty, since generally the assassins are freshly retired before being dragged back in for one last job...)
Is there any evidence that such a role has existed in modern times (say, since the end of WW2)?
I think there's a common-sense distinction between a movie-style assassin and a military sniper, a Mafia hit man, or a criminal thug:
- Killing is primary job description, not a by-product
- Does not decide on victim; is ordered / paid to perform assassination
- Is not directly involved with the victim (is "brought in to handle the job")
- Target is individual (different than a bomb-maker)
- Reason to believe they've assassinated more than once
The last point is to weed out either one-off intelligence assassinations or a willing-but-idiotic psycho who takes out a classified ad in "Soldier of Fortune."