Crom

Persistent Rage: Crom has the benefits of  a level 20 rage since the fight starts. (Damage upgrade + resistences)

Brutal Crítical: 6 dice rolls to critical attacks.

Frenzy: Crom attacks 3 times per turn

Relentless rage: If he drop to 0 hit points while you're raging and don't die outright, you can make a DC 10 Constitution saving throw. If you succeed, you drop to 1 hit point instead.

Each time you use this feature after the first, the DC increases by 5. When you finish a short or long rest, the DC resets to 10.

Celestial Axe. Melee Weapon Attack: +12 to hit, reach 5ft, one target. Hit: 4d10  of slashing damage +4d6 of radiant damage.

Choke. Grapple: 18 Strength saving throw. 6d8 damage per turn. 5ft

Elemental breath: 30 ft distance. 6d10 of  random element damage(Fire,Ice,Thunder)

Ancient Healing: Every time he avoid the dead, restores 100 life points.

Rage wave: When he receives a sneak attack or a critical, he can distortionate the space a little bit by screaming, reducing that damage to half.

4 Legenday actions.

Earthquacke: A gigantic rage scream causes an earthquake, causing 2d10 of bludgeoning to all enemies. Terrain 20 ft. In radius is difficult terrain. Strength,Dex and Con saving throw, at 12 of difficulty.

Plummet: When he has an enemy grappled, stamps his head against the floor. 6d10 damage.

Enforcer: Crom can turn his axe into a mace, hitting with 8d10 damage, ignoring armor class. If it fails, take half damage by a blast wave. Enemies in a 5ft range receive the blast wave damage. Cannot be blocked.

Glorious cutting wave: Hitting the floor with his axe, he can split the ground 30 feet in a straight line, causing 3d10  of radiant damage, 3d8 of bludgeoning damage. And the enemy need to pass an strength saving roll, with a difficulty of 18 to can move the next turn.(Only the next turn)