GROND, Orcish Siege Engine

All Orcs and Goblins you control have trample.
Whenever "GROND, Orcish Siege Engine" attacks, it gets +X/+0 until end of turn,
where X is the greatest power among creatures you control.
"GROND! GROND! GROND! GROND!"
- Sauron's Orc Army