The users of this ability can become the embodiment of violence, they can become more powerful when brutally fighting. The user can even cause bloodlust in every living thing the user comes across to enjoy the killing.
Sugilite (Steven Universe), the fusion of Garnet & Amethyst, but unstable that wreak havoc.
Roger Smith (American Dad!) becomes very violent in revenge quests, whether it be brutally killing 24 prison guards to escape or running down five teens over 20 dollars.
Kenpachi (Bleach) loves to fight, it became his life's purpose.
Due to his anger issues, Shizuo Heiwajima (Durarara) is introduced as a violent, no-nonsense tough guy, tending to throw vending machines and fight people who provoked him.
Broly (Dragon Ball Z) loves to kill and destroy, even for a Saiyan, killing his own father.
Katakuriko Matsudaira (Gintama) is called the "God of Destruction" because he is a violent nutcase who would use brutal weapons to deal with the simplest matters.
Kamui (Gintama) is the embodiment of the Yato tribe's violent ways, willing to kill family for reviving traditions and testing his own strength, living in the battlefield, and even punching Nobu Nobu for no good reason.
Wyzen's (Asura's Wrath) mantra affinity is violence.
Rose Tattoo (Image Comics) is popularly coined as the undying Spirit of Murder. More than capable killing anything and everything; including a neither living nor dead entity like The Eidolon.
Ernest Fairchilde/Evil Ernie (Eternity Comics) is the herald of megadeath and Lady Death's own personal agent of mass murder.
Doomsday (DC Comics) is the ultimate biological murder machine capable of living through and outlasting anything that can kill him. Ever adapting, always evolving until the day his very presence causes worlds to die.
Esdeath (Akame ga Kill) is the most sadistic murderess ever known.
Kaido (One Piece) is tyrannical leader of the Beasts Pirates, his power is only matched by his extremely brutal and bloodthirsty nature that craves only chaos.
Charlotte Linlin (One Piece) is the terrifying leader of the Big Mom Pirates, not even her own children is safe from her immense brutality.
Guts (Berserk), the Black Swordsman.
Ares (Marvel Comics) the God of War.
Conquest (Image Comics) was the worst and perhaps the most violent of Invincible's enemies...
...breaking Kid Omni-Man's jaw/arm and attempting to rip him in half...