Defender's heart (5e Feat)
From D&D Wiki
Prerequisites: 12 or higher Dexterity and proficiency in martial weapons
You can become a greater party tank for your allies.
When a creature misses an melee attack against you or an ally within 5 feet of you, you can use an reaction to counter attack.
When you hit an creature with a martial weapon, that creature's speed becomes 0 until the start of your next turn.
If you are wearing heavy armor holding a two handed martial weapon, increase your AC by 2.