Doom slayer

Those who emulate the archetypal Slayer seek the destruction of their foes, no matter how long that might take. Slayers pin-point weaknesses in their enemies and exploit them, brutally murdering their foes and reveling in the bloodshed

Rip and tear

Also at 3rd level, the more you attack a creature the more you learn about how to kill it in a devastating way. Whenever you hit a creature with an attack, you learn whether its current hit points are less than half of its maximum hit points, and whether or not its current hit points after the damage roll of the attack is low enough for you to perform a Glory Kill action against them.

When you are within 10 feet of a creature you can use your action to attempt to Glory Kill them. You move 5 feet toward that creature and if their current hit points are equal to or less than your fighter level + your proficiency modifier, you immediately reduce them to 0 hit points and regain hit points equal to their number of hit dice. A creature can only allow you to regain hit points in this manner once, regaining the ability to do so after it has completed a long rest. The movement as part of this action does not trigger attacks of opportunity. If their hit points are too high to allow you to successfully reduce their hit points in this manner, make an unarmed strike against them.

If the creature's hit points are reduced to 0 and they have an ability that would allow them to regain hit points, that ability is suppressed for 1 minute. Additionally, the creature's body is dismembered as part of the Glory Kill action if their hit points are reduced to 0. Lastly, if the creature's type is fiend or undead To Slaughter feature, double your fighter level when determining if you can immediately reduce their hit points to 0.

Praetor pathing

Once you've reached 7th level, your ability to find and reach your foes is improved. You gain a climb and swim speed equal to your movement speed, and your movement speed increases by 10 feet. You also ignore the effects of non-magical difficult terrain, and have resistance to any damage magical difficult terrain or any trap might deal to you. Lastly, you gain a +3 bonus to any attack roll or damage roll made against a door, wall, or similar structure.

blood punch

At 10th level, you can release blasts of energy from your fists. Once after completing a long rest, when you hit an enemy with an unarmed strike, you can deal double the damage and deal the damage to not just that enemy, but all enemies within a 15 foot cone behind the enemy. All enemies that take this damage must succeed on a Constitution saving throw with a DC of 8 + your proficiency bonus + your strength modifier or be stunned until the end of your next turn.

Once you use this ability, you cannot do so again until you complete either a short rest, or reduce three creatures to 0 hit points.

Unflinching

Starting at 15th level, your brutal nature gives you advantage on saving throws against being frightened or charmed. You are immune to being frightened or charmed by undead or fiends.

Aura of doom

Starting at 18th level, your presence prepares your enemies for death. You gain a 15 foot aura. When an enemy with less than half their maximum hit points within the aura takes damage from you, they have to roll a wisdom saving throw (8 + proficiency bonus + your charisma modifier) or become frightened of you for 1 minute. If a creature succeeds in the saving throw, it is immune to being frightened of you for till the end of the round. If the target is a fiend or undead, it has disadvantage on the saving throw.