Why is running water erosion so powerful?

All erosion is powerful, especially given millions of years. Running water is particularly powerful because the water cycle constantly causes Fluvial erosion globally, and it is the extent to which running water is found compared to the other agents which makes it so powerful. Rivers in particular are able to transport a lot of material, and the sheer force of a river, like the Amazon for example, means that it erodes far quicker than any other form of erosion.