Path of the Patron

Starting at level 3, a divine patron has acknowledged what you are fighting for and lends part of their power to your rage. The bond is not based on belief or worship, the patron simply approves of your choices and wishes to further them. This also means, that the patron's gifts can be withdrawn at any moment, if the Barbarian radically changes their behaviour or acts in stark contrast to their usual habit.
The connection can be a complete mystery to the Barbarian as well as an actual contract brought forth by the patron, depending on the patron and Barbarian. The patrons tend to be divine beings that favor purity and simplicity but otherwise they can be of any alignment. They want to further the Barbarian's cause, be it a noble fight for justice or simply a devotion to spread carnage. And they want the Barbarian to fight no matter the circumstances, depending on nothing but their bodily might and the powers gifted through their patrons.

Divine pugilist

As long as you are fighting unarmed, you can make to unarmed punches with each attack action (roll two attacks per attack action).
You are proficient at your unarmed punches and they deal 1d6+Str damage at level 3. This increases to 1d8+Str at level 8, 1d10+Str at level 12 and 1d12+Str at level 16.

At your DM's discretion, you may use gloves or similar items that do not count as weapons, to increase your damage. 

Blessed punch

Starting at level 6, your patron adds a magical quality to your unarmed punches. They now deal a type of magical damage fitting to your patron (chosen by the DM). If an opponent has resistance to that type of damage, they revert back to bludgeoning. 

Divine wrestler

Your patron grants power to your body, that seems incomprehensible to others. You can now grapple any creature aside from gargantuan without disadvantage and gargantuan ones with disadvantage. 

Additionally, when you hold a creature grappled, you can choke them for 1d12+STR on each of your turns using a bonus action (increasing to 2d12+STR at level 12 and 3d12+STR at level 16).

Guided punches

Your patron guides your punches, leading them to vulnerable points more often than usual.

All your punches now score critical hits at 19 as well as on 20. This guidances deepens at level 16, from where on an 18 also counts as a critical hit.

Live for the punch

Once per day you can use a bonus action to channel the essence of your patron directly into one of your punches, dealing immense damage and healing you in the process.

Once a day, if a punch hits a target, you can choose to inflict 12d12+Barbarian level damage (of the type granted by Blessed punch or bludgeoning) and heal yourself by the same amount, using a bonus action.