Nouns

(n)killer, slayersomeone who causes the death of a person or animal
(n)cause of death, killerthe causal agent resulting in death“heart disease is the biggest killer in the United States”
(n)killera difficulty that is hard to deal with“that exam was a real killer”
(n)killer whale, killer, orca, grampus, sea wolf, Orcinus orcapredatory black-and-white toothed whale with large dorsal fin; common in cold seas