You’ve developed a unique fighting style that uses momentum to keep enemies on their heels.
Always Be Moving
At 3rd level, you do not provoke attacks of opportunity as long as you move at least 10 feet immediately after the attack of opportunity would be provoked. Additionally, if you move at least 10 ft directly before making an unarmed attack or attack with a Brawler Weapon, you can attempt to shove the creature as part of the attack. On a hit, the target must make a Strength Saving throw versus your Brawl Save DC or be pushed 10 ft in the direction of your movement path and knocked prone. If the shove succeeds, you can immediately move an additional 10 feet without provoking attacks of opportunity.
Kinetic Flow
At 6th level, your constant motion allows you to maneuver around enemies with ease. When you move at least 10 feet before making an unarmed or Brawler weapon attack, you gain the following benefits until the start of your next turn:
You gain temporary hit points equal to your Dexterity modifier + your proficiency bonus.
Your AC increases by 3.
Additionally, when you successfully shove a creature as part of your Always Be Moving feature, you can immediately leap up to 10 feet in any direction as part of the same attack, ignoring difficult terrain and without provoking attacks of opportunity.
Momentum Blows
Speed equals force, a concept you know well. At 10th level, if you move at least 10 ft before making an unarmed or Brawler weapon attack, you deal additional damage on a successful hit. The additional damage starts at 1d6 and increases by one die size for every additional 5 ft of movement before the attack, up to a maximum of 2d12. If you hit multiple creatures with separate attacks during the same turn, the Momentum Blows damage applies to each attack based on the total movement made during that turn.
Revved Up
Once you get moving, it’s hard to stop you. At 14th level, effects that would reduce your movement speed are halved (rounded up to the nearest 5 ft increment), and you have resistance to effects that would cause the restrained or grappled conditions. Additionally, after you make an unarmed or Brawler weapon attack, you can move up to 10 feet as a free action without provoking attacks of opportunity.
Line Drive
You are unstoppable once you get going. At 18th level, if you use your entire movement speed to move in a straight line, you can choose to make an attack against each creature in the path of your movement. If you do so, calculate Momentum Blows’ damage based on the total distance moved before the first attack, and apply this damage to all subsequent attacks made during that movement. After completing all attacks, you can continue moving up to half your movement speed in the same direction, ignoring difficult terrain and obstacles that are Large or smaller.