Shadow Hunter

I wanted a full bounty hunter who hunts in the shadows and rather than Multiclassing I figured this may work as a brand new Subclass. I really liked the elements of hiding in the shadows and using the darkness as a weapon with the Gloom Stalker Ranger. But obviously a bounty hunter fit the Rogue class a lot better and getting sneak attack for something attacking in the shadows made sense.

Shadow Hunter Rogues live for the darkness constantly looking for ways to hide and surprise their prey. They are a master at killing a single creature as fast as possible, but if they get discovered and the battle rages on they may try and use their expert maneuvers to get away or find another killing blow. These expert killers are often bounty hunters or assassins priding themselves on landing one death blow and escaping undetected. They often find themselves more as a lone wolf type of player but can function within a team often as a scout or someone who may hide on their own waiting to ambush the strongest of the enemies. No opponent is too much for a Shadow Hunter as long as they can get the edge hiding and are undetected, no one can match their speed and stealth with a quick kill.

Molded by Darkness

When you choose this Archetype at 3rd level, you begin to feel at home in the darkness. You gain dark vision to a range of 60 feet, if you already have dark vision its range increases by 30 feet. You also have advantage on Dexterity (Stealth) checks when in darkness. 

Shadow Slayer

Starting at 3rd level, while in darkness, you are invisible to any creature that relies on dark vision to see you in that darkness. As well as a hit you land on a creature that cannot see you or is surprised is considered a critical hit.

One Hit Hunter

Starting at 9th level, you are always looking to end a fight before it even gets a chance to start. Because of this you have mastered ambushing tactics to make kills swift and without a trace. 

You have a bonus to your initiative rolls equal to your Wisdom modifier. At the start of your first turn of combat your walking speed increases by 10 feet, which lasts until the end of that turn. If you take the Attack action on that turn, you can make one additional weapon attack as a part of that action. As well as you have advantage on attack rolls against any creature that has not taken a turn in the combat yet.

Stubborn Killer

At 13th level, you have become accustomed to landing your strikes with precision that when you miss you can turn it into another attack. Once on each of your turns when you miss with a weapon attack, you can make another weapon attack as part of the same action. This second attack cannot use the function of your sneak attack.

Umbral Ambush

When you reach 17th level, you have mastered the hidden attack. When you attack a creature that cannot see you in the dark you have advantage on the attack and on a hit it must make a Constitution saving throw (DC 8 + your Dexterity modifier + your proficiency bonus). On a failed save, double the damage done to the creature for that hit.