Mr. Kill

Noun.

Someone who can take out an entire gang of people in 5 minutes or less. Their weapon of choice is usually a gun or any edged weapon.
Female Mr. Kills are known as Mrs. Kill or Ms. Kill

Some famous Mr. Kills are:

Rich Evans
Chuck Norris
Rick Moranis with a gun
John Rambo
Doom Guy (also known as the Doom Slayer)

Guy 1: Dude! I just wiped out a battalion of Somali Pirates!

Guy 2: Dude, you've just achieved the status of Mr. Kill.