Executioner

Bonus Proficiency

When you choose this archetype at 3rd level you gain proficiency in the Intimidation skill, if you are already proficient in it your proficiency bonus is doubled for checks you make with it.

Path to the Gallows

Starting at 3rd level, you can render your enemies hepless putting them on the optimal position to strike the final blow. When you hit a creature with a weapon attack on your turn, you can force that creature to make a Strength saving throw DC = 8 + your Strength modifier + your proficiency bonus. On a failure the target has its speed reduced to 0 and you have advantage on attack rolls against it until the end of your next turn. You can use this feature a number of times equal to your Strength modifier and you regain all uses once you finish a long rest.

Execution

Also at 3rd level you can deal a devastating blow to your enemies while they are most vulnerable, potentially ending their lives. Once on your turn, when you hit a creature with a weapon attack while you have advantage and the target's speed is 0, you can choose to roll a d20, if the roll is equal to or lower than your fighter level the attack scores a critical hit.

Swift Mercy

Beginning at 7th level you can efficiently dispose of multiple targets at once, when you reduce a creature to 0 hit points or when you score a critical hit, you can use your bonus action to move up to half your speed and make one weapon attack.

Inescapable End

At 10th level very few are capable of avoiding your sentence. Creatures provoke attacks of opportunity from you whenever they cast a spell or produces an effect that would allow them to move or teleport away from your reach, if the attack of opportunity hits the spell or effect fizzles and the creature remains in the same space. Additionally you have advantage on opportunity attacks.

Death Dealer

Starting at 15th level when you use your action surge, you can use your execution feature up to twice that turn without needing to fulfill its conditions.

Final Blow

When you reach 18th level, your strikes become a guaranteed death sentence. When you score a critical hit while the target is at or below half their hit point maximum, you can force the target to make a Constitution saving throw, DC = 8 + your Strength modifier + your proficiency bonus. If it fails it is reduced to 0 hit points. If it succeeds it is stunned until the end of your next turn. Once you use this feature you can't use it again until you finish a long rest.