Undead Hydra

Deathtouch, Haste, Hexproof, Indestructible, Trample.
At the beginning of your upkeep, put a +1/+1 counter on this creature.
Other Hydra and Zombie creatures you control get +1/+1 for every +1/+1 counter on this creature.
Whenever this creature kills another creature your opponent controls, put a 2/2 Zombie creature token onto the battlefield.