Deus Ex Machina: Kill Anna or Gunther with their killphrase (just a word or two that instantly kills them). It may not be "brutal" but it's certainly harsh, cold, and simply mean.
Metal Gear Solid 3: Set the time on the PS3 ahead a couple years and The End actually dies of old age just waiting for you to come and fight him. Once again, maybe not brutal in the traditional sense, but it's still a horrible thing to do.
Metal Gear Solid 3: Sneak up on a soldier and hold him up. Grab him and press R3 to interrogate him. every time he tries to speak, choke him. Finally, do it one more time, but slit his throat as he's speaking.
Metal Gear Solid 3: When you're at the docks, knock a soldier out, then shoot him in the leg. Drag him to the end of a dock...then just let him wake up. When he stands up, he automatically falls into the water and drowns.
Metal Gear Solid 3: Throw a live poisonous snake at a soldier. Muahahaha
Metal Gear Solid 3: Set the time on the PS3 ahead a couple years and The End actually dies of old age just waiting for you to come and fight him. Once again, maybe not brutal in the traditional sense, but it's still a horrible thing to do.
Metal Gear Solid 3: Sneak up on a soldier and hold him up. Grab him and press R3 to interrogate him. every time he tries to speak, choke him. Finally, do it one more time, but slit his throat as he's speaking.
Metal Gear Solid 3: When you're at the docks, knock a soldier out, then shoot him in the leg. Drag him to the end of a dock...then just let him wake up. When he stands up, he automatically falls into the water and drowns.
Metal Gear Solid 3: Throw a live poisonous snake at a soldier. Muahahaha