How can you remove spray painted graffiti from concrete?

Usually a high powered pressure washer will take off paint rather easily. Hope this helps. Depending on the pressure of the washer, yes some residential/consumer pressure washer moderls can do it. Industrial/professional water blasting machines [some can go to 20,000 to 30,000 pounds of pressure] can remove anything from concrete, INCLUDING THE CONCRETE. So, if you cannot get the paint off with a consumer model, and you just "have" to get it off, consider engaging a commercial/industrial pressure washing contractor.