General terms:
* φόνος (phonos): This word literally means "murder" or "killing" but can also be used to refer to the person who commits the act.
* δολοφόνος (dolophonos): This word specifically refers to a murderer, someone who kills intentionally and unlawfully.
* ανθρωποκτόνος (anthropoktonos): This means "manslayer" or "murderer of humans."
More specific terms:
* αυτοκτονία (autoktonia): Suicide, the act of killing oneself.
* εγκληματίας (englimathias): Criminal, someone who commits a crime (which could include murder).
* φονιάς (foniás): This is a more colloquial term for "killer," often used in a negative sense.
The best choice depends on the specific situation and the intended meaning.