Action Surge. On his turn, he can take one additional action. He can use it twice before a short or long rest, but only once on the same turn.

As an action, he can unleash a 30-foot cone of destructive energy from his weapon. Each creature in that area must make a DC 16 Dexterity saving throw, taking 8d6 lightning damage on a failed save, or half as much damage on a successful one. Once this action is used, it can't be used again until the next dawn.

Indomitable. He can reroll a saving throw that you fail. He can use this feature three times between long rests.

Legendary Resistance (1/day). If Smasher fails a saving throw, he can choose to succeed instead.

Multi-Attack. Adam Smasher gets 3 attacks.

Unarmed Strike. Melee Weapon Attack: +8 to hit, reach 5 ft., 1 target. Hit: 8 (1d6 + 4) bludgeoning damage.

Tsunami Arms Helix. Ranged Weapon Attack: +10 to hit, range 80/240 ft., 1 target. Hit: +15 (2d8 + 6) piercing damage, +7 (2d6) lightning damage.

Second Wind. He can use a bonus action to regain hit points equal to 1d10 + 10. Once he uses this feature, he must finish a short or long rest before he can use it again.

Adam Smasher can take 2 legendary actions.

Hellbringer (Costs 1 Action). He can throw a grenade at a point up to 60 feet away. Each creature with 20 feet of an exploding fragmentation grenade must make a DC 15 Dexterity saving throw, taking 5d6 piercing damage on a failed save, or half as much damage on a successful one.