Killer (TV series), a 2021 South Korean television series.
The Assassin Next Door (2019 Korean Drama), also known as the Killer, based on the webtoon series My Neighbor, the Killer.
The Killers, an American rock band.
The Murderers Among Us (or The Killers) from *Among Us*.
In general, "killer" could also refer to various criminals who commit murder, like serial killers or hired assassins. These meanings could vary based on different circumstances and contexts.