Killer
From SA Mafia Wiki
A Killer is a role with a limited nightkill. The Killer receives requests for kills from a Boss, but it is left to the Killer's discretion whether they perform the kills or not.
The Killer can always reject requests to kill themselves, but might have limited rejection power otherwise. A Killer can sometimes perform as many kills as there are requests if there are multiple Bosses in a game, or, alternatively, a single Boss can submit multiple requests a night and the Killer decides which to perform.
The Killer is not to be confused with the similarly-named Serial Killer.