Base Class: Rogue
You never bothered to deal with the mundane usage of blades, for why would you?
You are a street brawler or perhaps a prized champion in the dark underworld. And in places like these only one type of weapon count, Your own body.
Seasoned Fighter
Starting at 3rd level, your unarmed strikes hit harder. Your unarmed strikes now deal 1d4 damage. And you may make these attacks with Dexterity instead of Strength for the attack and damage rolls. If you hit a creature with your strike you may make another strike with your bonus action.
Your unarmed strikes counts as finesse for the purpose of applying sneak attack.
Skilled brawler
When you choose this archetype at 3rd level, you gain proficiency in the Athletics skill if you don’t already have it. Your proficiency bonus is doubled for any ability check you make that uses this proficiency.
Additionally, you have advantage of checks made to escape an enemy grapple.
Improved Strikes
At 9th level, your unarmed strikes deal a 1d6 in damage.
Also whenever you try to shove a creature with your action, if you win contest, they are knocked back 5 feet and knocked prone. If you succeed you may make an unarmed strike with your bonus action.
Wrestle Master
Starting at 13th level, you become quite adept at keeping out of harms way, whilst also making things difficult for a grappled foe.
During a grapple, all attacks from everyone except the grappled foe have disadvantage against you. Also during a grapple you give advantage to your allies against the grappled enemy.
Finishing Blow
Starting at 17th level, If you grapple a creature you may strike him as a bonus action. If this hits the target is subjected to both a critical and a sneak attack.
This feature can only occur once per turn.