Mafia III

This achievement can be done at any time during your playthrough against hostile enemies or even cops. After the first few story missions the game will introduce Brutal Takedowns. These takedowns can be done at the end of a melee combo by holding and releasing when the mini on-screen meter hits the "sweet spot" of the QTE prompt.

In order to earn this achievement, you'll have to do three of these finishers in a row with no other kills in between. This is best done in a dense crowd of enemies with plenty of Adrenaline Shots on hand to prevent yourself from dying. The achievement will unlock after the third Brutal Takedown provided no other kills were registered in between takedowns.