Begin with a list of big or powerful things. Big ideas, big people, big concepts. Godzilla, The Grim Reaper, God (in whatever form you prefer), Love, The World Tree, Frost Giants (ok, they invaded from yesterday's exercise, sue me), Hades, Tartarus, the ocean, nuclear weapons.
Think big. The universe.
Now, write a poem about what they can't do.
Can they tie their shoes? Take the dog for a walk? Color inside the lines? Communicate with their worshippers about what really are or aren't its true ideals and what to do when people mistake the symbols it's left behind?
Start small or start big with the details. What really frustrates this person, thing or concept? If you went with a grand idea, feel free to anthropomorphize the idea... or don't. Whatever gets you the most mileage.
No matter how powerful we think something is, or might be, there's always something beyond its conrol.
Read On Death, Without Exagerration, by Wislawa Szymborska over at Nobelprize.org. Oooh, fancy shmancy with our links today, aren't we?