Just one colossal power.
The ability to quickly, easily edit all elements of reality in all dimensions including space and time while maintaining personal immunity to the consequences of such edits.
Thus, I could modify the gravitational constant G on a whim. I could decide that a poster's great grandmother should have had blond hair instead of brown hair, and would give him a silver shilling with the word "rosebud" scratched on the face back in 1947. Or, I could decide that the supernova which created the Crab Nebula went off so I could watch it tomorrow evening instead of whenever it actually occurred.
So, how to solve the current problem with overpopulation? Back in the early 1950's, the U.S Agriculture department came up with the Green Revolution, which increased crop yields a lot. Arguably, it began in the mid-1940's when US Vice-President Henry Wallace took a tour of Mexico and, with Ford Foundation funding, helped them increase yields.
So, instead, Mr. Wallace would have had more interest in the hardships of residents of Appalachia. He would never have gone to Mexico, USAID would not have created the Green Revolution - and so the population of the Earth would be at 2 billion instead of 6.5 billion. Thus I would have deleted 4.5 billion people without screwing up my karma any worse than it already is.
How's that for a power?
