Hostage

3rd-level Agent feature 

Whenever you choose the Grapple option when making an unarmed strike, you can make it a Bonus action instead of an Action. Additionally, if you are able to grapple a creature on your turn, as a part of the same action, you can attempt to make them your Hostage by making a Charisma (Intimidation) check contested by the creature's Wisdom (Insight) check. If your score was higher than the creatures, they now become your Hostage. A Hostage has the Charmed condition for as long as you have them grappled and cannot make any attempt to escape your grapple. You also gain no movement penalties when moving the grappled creature. You can attempt to make the creature your Hostage once on each of your turns

You also gain proficiency in Intimidation.

Silent But Deadly

3rd-level Agent feature

You gain the following abilities:

Neutralize: You can take a bonus action to try to choke Unconscious a creature you currently have grappled. The creature must succeed on a Constitution saving throw with a DC of 8 + your proficiency bonus + your Dexterity or Strength modifier (whichever is highest) or be knocked unconscious on a failed save. Once knocked out, the creature starts a Short Rest and stays unconscious for 10 minutes. The creature regains consciousness if it takes damage or if another creature spends its Action to reawaken it. You can use this ability a number of times equal to your Dexterity modifier (minimum of once) per Long Rest.

Precise Strike: Whenever you deal damage using a damage type to a creature that has vulnerability to that damage type, you can use your sneak attack against that creature without needing advantage. The rest of the Sneak Attack rules still apply.

Stunner

9th-level Agent feature 

You gain the following Cunning Strike option

Stun (Cost: 2d6). A creature must succeed a constitution saving throw or be stunned for 1 minute. The creature can repeat the saving throw at the end of each of its turns to end the condition.

Undetected

13th-level Agent feature

You continue to go unnoticed when sneaking up on creatures. You cannot be detected by a creature's Blindsight or Tremorsense. Additionally, you gain Blindsight with a distance of 20 ft.

Covert Tactics

17th-level Agent feature 

You know how to pick apart a group of enemies, one by one. Whenever you roll for initiative, you can choose a number of hostile creatures equal to your Dexterity modifier that you can see within 60 ft of you. These creatures now gain vulnerability to one of the given damage types of your choice: Piercing, Slashing, or Bludgeoning.  Additionally, if you deal the killing strike to one of your marked targets, you can mark another creature within 15 ft of the killed target to give it the same vulnerability. A marked creature keeps this vulnerability until you deal damage using a damage type different from the damage type you gave the creature vulnerability to.