Intimidating Roar

Enchant target creature.
If the enchanted creature is the strongest creature
in play, give every opponents creature -1/0.
If the enchanted creatures power and toughness
equals 20 or higher, give every opponents creature
-3/0 and cant block enchanted creature.
When enchanted creature dies, Obliterate me.
Every fiber of their being told them to do not
but one thing... Run