Reaper

Some fighters spent long times of their life on the battlefield. They come so close to death that they stop fearing it and become an imbodiment of death themselves. This is how reapers are born. 

Death Bringer

Beginning when you choose this archetype at 3rd level, whenever you bring a creature to 0 hitpoints with a weapon attack you may as a reaction move to another creature within 30 feet and make a weapon attack with advantage.

Chains of Death

Starting at 7th level, you can pull creatures literally closer to death by using chains and ropes attached to your weapons. Whenever you hit a creatue within 30 feet with a ranged weapon you may make a contested Athletics (strength) check to pull the creature within 5 feet of you.

Near Death Experience

At 10th level, you can still use your action when you are unconscious and have succeeded a death saving throw. You remain prone and have a movement speed of 0 while unconscious.

Living on the Edge

Starting at 15th level, you are most lethal when you are near death yourself. Whenever the amount of your remaining hitpoints is lower than your Armor Class all your melee weapon attacks deal an extra 2d10 damage.

Soul Shield

At 18th level, you attain the ability to use the souls of the dead to protect yourself. When you kill a creature within 15 feet of you, you are immune to damage untill the start of your next turn.