Bloated Zombie

Undead Fortitude. If damage reduces the zombie to 0 hit points, it must make a Constitution saving throw with a DC of 5 + half the damage taken, unless the damage is radiant or from a critical hit. On a success, the zombie drops to 1 hit point instead.

A Host To Many: When the bloated zombie reach 0 hit points if it fails its undead fortitude saving throw, it's body expands exponentially and from it several lesser undead spawn from its corpse, attacking anything nearby.

Crush. Melee Weapon Attack: +6, reach 5 ft., one target. Hit: 14 (2d10 + 4) bludgeoning damage

Bite. Melee Weapon Attack: +6, reach 5 ft., one target. Hit 11 (3d8 + 4) bludgeoning damage

Furious Charge. The Bloated Zombie makes a mad charge in one direction for its full movement or until it hits a static object, each creature within 5 ft of its charge must make a DC: 14 Dexterity saving throw. If a creature succeeds on the saving throw they take half damage and are not knocked prone, however, if a creature fails its save they take 16 (4d6 + 4 ) bludgeoning damage and are knocked prone.

A creature directly in the line of the charge that fails this check is carried with the zombie to its location, and takes an additional 1d6 damage, as it is thrown from the creature body to the floor or smashed against a wall.

The Bloated Zombie has 3 legendary actions, these actions recharge every at the start of each round.

Parasitic Grapple (Costs 1 Action). The Bloated Zombie allows the many undead it has in its from to stretch forth and grapple any creature within 5 ft of it. 

Sweeping Attack (Costs 2 Actions). The Bloated Zombie swings its arms in front itself in a 15ft radius, any creature within range must make a DC: 14 Dexterity saving throw, or take 14 (2d10 + 4) bludgeoning damage and is knocked prone