What is a slang term for killer?

There are many slang terms for "killer," depending on the context and desired tone. Here are a few examples:

Neutral:

* Hitman

* Assassin

* Executioner

Informal:

* Whacker

* Gunman

* Triggerman

* Enforcer

More informal/street slang:

* Juice

* Snatcher

* Cold-blooded

* Grim Reaper (figurative)

Humorous:

* Liquidator

* Life-shortener

* Professional problem solver

Remember that the appropriate term depends on the context and the intended audience.