Thug

Ruthless Ruffian
Beginning at 8th level, when you have dealt Sneak Attack damage to a creature on your current turn, you can use your bonus action to attempt to viciously intimidate that creature. Make a special Intimidate check contested by the target's Wisdom save. If you win the contest, that creature is Frightened of you until the end of your next turn. Additionally, you gain Advantage against any creature afflicted with the Frightened condition, gain proficiency with shields, and can treat any non-Heavy bludgeoning weapon with which you are proficient as a finesse weapon.

Kneebreaker
Beginning at 13th level, when you deal sneak attack damage to a creature, you half that creature's base walking speed until the end of your next turn. Additionally, when you inflict the frightened condition on a creature, you can choose to cripple it with fear. Doing so allows the creature to move towards you freely, but prevents it from moving away.

Vicious Example
Beginning at 18th level, whenever you land a critical hit or reduce an enemy to 0 HP, you may make a special Intimidate check contested by the Wisdom save of enemies within 60'. Each enemy that loses the contest to you is Frightened of you until the end of your next turn.