Cal, the Gloved Baldy

Gloved Might. Cal’s unarmed strikes count as magical and ignore resistance to bludgeoning damage 

Serious Mode (1/Day). As a bonus action, Cal enters Serious Mode for 1 minute. While active: His Punch becomes One Punch. He can use Multiattack with One Punch. He gains resistance to all damage. His speed increases by 20 ft. He has advantage on all attacks and saving throws.

Multiattack. Enter Cal makes two melee attacks — either Punch or One Punch, depending on his mode.

Punch. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 19 (2d10 + 8) bludgeoning damage. Target must succeed on a DC 18 Strength saving throw or be pushed 10 ft. and knocked prone.

One Punch (Serious Mode). Melee Weapon Attack: +12 to hit, range 5 ft., one target. Hit: 86 (12d12 + 8) force damage. If the target has 60 HP or fewer after taking damage, it is instantly knocked unconscious (DC 18 Con save at the end of each of its turns to awaken). Non-magical objects and structures in a 10 ft. radius are instantly destroyed.

Legendary Actions (2 Actions per round)

Step In (Costs 1 Action). Cal moves up to his speed without provoking opportunity attacks.

Stare Down (Costs 1 Action). One creature Cal can see within 30 ft. must succeed on a DC 16 Wisdom save or have disadvantage on its next attack.

Combo Flick (Costs 2 Actions). A creature within 5 ft. must succeed on a DC 18 Constitution save or be stunned until the end of its next turn.