Street Fighter

An Elf cracks her knuckles in an Alleyway and grabs a nearby brick as a thug walks towards her. She acts swiftly, sweeping out his legs from underneath him. As he tries to get up, she pulls his shirt up and down, blocking his vision as she swiftly knees him in his gut, causing him to double over before she shoves him back down onto the ground and slams the brick onto his skull with a sickening crunch.

A Dwarf shoves a Genasi to the ground before smashing a bottle open on her stomach. As she curls up in pain and lashes out, the Dwarf partially dodges one of her strikes, minimizing the damage as he delivers a brutal stab to her gut using the now broken bottle within the same movement, sending her reeling and back onto the ground.

A Goliath tries to trap a Human in a bear hug, but the human expertly ducks out of the way, slipping behind the Goliath turning the tables as suddenly the Goliath herself is trapped within their vice like choke hold, the human restricting her movement by slamming a foot against the back of her knees, forcing her onto her knees, and right down into their Aasimar companions waiting blade.

A Street Fighter is an unorthodox kind of Rogue. Easily mistaken for a Monk, Fighter or even Barbarian, these Rogues are set apart by one thing: Their mentality. They will do absolutely anything to best their foe. Tripping, throwing sand into their eyes, restraining them and cheap shots are their expertise. Against a creature of similar size, a Street Fighter and their vast arsenal is to be feared and respected, or the foe will be down on the ground with a improvised weapon sailing for their head before they can even react.

Underhanded Tactics

When you choose this Archetype at 3rd Level, you have adopted a simple mentality: A Victory, no matter the means, is still a Victory.

When you take this archetype, you have dedicated yourself to fighting dirty, and making the best of the worst situations that you find yourself in. In the right hands, anything is a weapon. You gain proficiency with Improvised Weapons, and your Unarmed Strikes and Improvised Weapons that you wield both now have the Finesse property, and now deal 1d4 damage on a hit. This dice scales with your Rogue level, increasing to 1d6 at 9th Level, and 1d8 at 17th Level. If you have the Martial Arts feature from Monk, your unarmed strikes will use whichever dice is higher. However, your improvised weapons will always use your Street Fighter Dice.

You additionally gain the ability to use your Cunning Action to try and Grapple a creature, or try and shove them prone. Your Methods of Fighting are very underhanded, and you will do anything you can to win.

Strengthened By The Streets

At 3rd Level, your intensive training has hardened your Body and pushed it to it's absolute limit.

Your hit point maximum increases by 3, and increases by 1 each time you take a level in this class.

Uncanny Counter

At 9th Level, you learn how to dodge just in time to minimize the damage an opponent does while using that time frame to strike back.

Whenever you take the Uncanny Dodge reaction, you can now make a weapon attack against the creature who attacked you if they are within range, or choose to attempt to grapple them instead. Any attacks you make using this reaction cannot benefit from your Sneak Attack Feature.

Additionally, you've become more confident with your style of fighting, and now know how to utilize your momentum and agility to devastating effect. Whenever you roll to Grapple a creature or Shove them prone, You can roll Acrobatics rather than Athletics for the check if you so choose. 

Slippery

Starting at 13th level, your expertise with grappling other creatures has made you much harder to pin down in one spot, and you escape from the grasps of other creatures with ease

You now have advantage on saving throws and checks to escape the effects of the Grappled and Restrained conditions. Additionally, when you escape one of these effects, you can immediately use your reaction to move up to half your movement speed without provoking attacks of opportunity, or choose to attempt to grapple or shove the creature that was grappling you.

Heavy Hitter

At 17th level, your skill in your dirty style of fighting and your dishonest tactics have enabled you to be able to knock your opponents down, and make sure they stay down.

When you hit an prone or grappled enemy, your sneak attack deals an additional 3d6 damage if it's applicable.

Once per Short or Long Rest, when you hit an enemy with your sneak attack and they are not already prone, you can force them to make a Strength Saving Throw (The DC is 8 + Your Proficiency Modifier + Your Dex Modifier) or be knocked prone, and take disadvantage on their attack rolls until the end of their next turn, whether they stand up or not.