Rage. As a Bonus Action Vitali enters a rage for 1 minute. During this rage Vitali has resistance to all damage except psychic damage. He adds +4 damage to all strength based attacks. And he has advantage on all strength ability checks and saving throws. 

Reckless Attack. When Vitali makes an attack, he can choose to gain advantage on the attack roll, at the cost of all attacks on him having advantage until the start of his next turn. 

Danger Sense. Vitali has advantage on Dexterity Saving Throws that he can see the source of. 

Feral Instincts. Vitali has advantage on initiative rolls, and cannot be surprised. 

Brutal Critical. Vitali rolls an 3 additional damage dice when determining the extra damage for a critical hit with a melee attack.

Relentless Rage. If Vitali drops to 0 hit points while he is raging and doesn’t die, he can make a DC 10 CON saving throw. If he succeeds, he drops to 1 hit point instead.

The DC increase by 5 each time he uses this after the first, resetting to 10 after a short or long rest.

Indomitable Might. If the total on a strength check or saving throw is less than 30, Vitali can use 30 as his result instead. 

Multi Attack. Vitali makes two attacks with the Hammer of Thunderbolts.

Hammer of Thunderbolts Melee Weapon Attack: +18 to hit, reach 5 ft.. Hit: (2d6 + 25) bludgeoning damage. 

Hammer of Thunderbolts. RangedWeapon Attack: +18 to hit, range 20/60 ft., 1 target. Hit: (2d6 + 25) bludgeoning damage, all creatures within 30 feet of this target must make a DC 24 Constitution Saving Throw, on a failure they take (4d10) thunder damage, and are stunned. 

Great Weapon Master. If Vitali reduces a creature to 0 hitpoints, he can make an additional attack as a bonus action. 

Stone's Endurance. As a reaction Vitali can reduce any damage he takes by (1d12+10).