At 3rd level, you gain one of the following features of your choice. 

Colossus Slayer

Your tenacity can wear down the most potent foes. When you hit a creature with a weapon attack, the creature takes an extra 1d8 damage if it’s below its hit point maximum. If the creature is bloodied it instead takes an extra 2d8 damage. You can deal this extra damage only once per turn.

Giant Killer

When a Large or larger creature within 5 feet of you hits or misses you with an attack, you can use your reaction to attack that creature immediately after its attack, provided that you can see the creature.

Note: extra damage dice? (Maybe per size difference)

Horde Breaker

Once on each of your turns when you make a weapon attack, you can immediately make another attack with the same weapon that only targets a creature within range of your weapon that wasn’t hit by the original attack.

At 7th level, you gain one of the following features of your choice.

Escape the Horde

Your movement does not trigger opportunity attacks

Multiattack Defense

When a creature hits you with an attack, you gain a +4 bonus to AC against all subsequent attacks made by that creature for the rest of the turn.

Steel Will

You have advantage on saving throws against being frightened or charmed. 

When you fail a save against being frightened or charmed you may instead choose to succeed. Once you have used this ability to succeed a saving throw, you cannot use it again until you complete a long rest.

At 11th level, you gain one of the following features of your choice.

Volley

Once on each of your turns you can use an action to make a ranged attack against any number of creatures within 10 feet of a point you can see within your weapon’s range. You must have ammunition for each target, as normal, and you make a separate attack roll for each target.

Whirlwind Attack

Once on each of your turns when you make the attack action with a one-handed melee weapon you can attack twice rather than once with that weapon.

At 15th level, you gain one of the following features of your choice.

Stand Against the Tide

When a hostile creature misses you with a melee attack, you can use your reaction to force that creature to repeat the same attack against another creature (other than itself) of your choice.

Uncanny Dodge

When an attacker that you can see hits you with an attack, you can use your reaction to halve the attack’s damage against you.