Rage. With a bonus action Akuma can rage adding +4 to damage rolls and resistance to slashing, bludgeoning, and piercing from nonmagical attacks.
Devil's Rage. Akuma's thirst for combat is nearly impossible to manage, if raging and Akuma would drop to 0 hit points he drops to 1 hit point instead of can immediately make an attack with any ability on a target within 10ft.
Devil's luck. Akuma has advantage on saving throws against magical affects
Brutal Critical. On critical strike Akuma does an additional die of damage
Multiattack. Akuma makes three melee attacks or two ranged attacks.
Unarmed Strike. Melee Weapon Attack: +8 to hit, reach 5ft, one creature. Hit: 13 (2d8 + 4) magical bludgeoning damage. If the target is Medium or smaller creature it must succeed on a DC 18 Strength saving throw or be knocked prone. If Akuma knocks a creature prone this way it may immediately make an additional attack on the creature
Hadou Blast. Ranged Weapon Attack: +7 to hit, reach 120ft, one target. Hit: 20 (3d10+3) force damage.
Hadou Beam (recharge 5-6). Ranged Weapon Attack: +7 to hit, reach 60ft beam. Hit: 30 (6d8) magical fire damage. Target must succeed on a DC 15 DEX saving throw taking half damage if doing so.
Whirlwind blow. Melee Weapon Attack: +8 to hit, reach 5ft. Hit: 13 (2d8 + 4) magical bludgeoning damage. Targets all adjacent creatures.
Parry. Akuma adds 4 to its AC against one melee attack that would hit it. To do so, the Akuma must see the attacker. If this causes the attack to miss Akuma may immediately make an unarmed attack against the attacker
Akuma has 3 legendary actions that reset on its turn
Relentless Onslaught (cost 3 actions): Akuma may move it's full movement speed and use it's multiattack action to make three unarmed strikes
Devil's Step (cost 2 actions) : Akuma may move it's movement speed without taking attacks of opportunity
Legendary Resistance 3/day: If Akuma would fail a saving throw it may succeed it instead