Berserker Chief

Reckless. At the start of its turn, the berserker can gain advantage on all melee weapon attack rolls during that turn, but attack rolls against it have advantage until the start of its next turn. 

Battle Hardened. Gain 2 HP for every hit die and maximize each die. 

Natural Armor. Add constitution modifier to AC.

Charger. If you move at least 10 feet in a straight line immediately before taking this bonus action, you either gain a +5 bonus to the attack's damage roll (if you chose to make a melee attack and hit) or push the target up to 10 feet away from you (if you chose to shove and you succeed). 

Sentinel.  When you hit a creature with an opportunity attack, the creature's speed becomes 0 for the rest of the turn.
Creatures provoke opportunity attacks from you even if they take the disengage action before leaving your reach.
When a creature within 5 feet of you makes an attack against a target other than you (and that target doesn't have this feat), you can use your reaction to make a melee weapon attack against the attacking creature.

Multiattack. Make two attacks with Greataxe. 

Greataxe. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 9 (1d12 + 3) slashing damage.

War Cry (Recharge 6). The Berserker Chief lets out a loud shout attracting other Berserkers in the area to him and rallying his allies to battle. Summon 2d4+2 Berserkers to his location to aid him in battle. 

The Berserker Chief can take 1 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The Berserker Chief regains spent legendary actions at the start of its turn.

Move. The Berserker Chief moves up to its speed without provoking opportunity attacks.

Greataxe attack. The Berserker Chief makes Greataxe attack.