Willpower rhymes with:
airpower, brainpower, firepower, horsepower, manpower, seapower, airpower, belflower, bellflower, brainpower, cauliflower, coneflower, cornflower, eisenhower, fillauer, firepower, hightower, horsepower, hufbauer, icenhower, landauer, manpower, mayflower, safflower, seapower, sunflower, wallflower, wildflower, zembower
Willpower sounds like:
walbro, wallpaper, welfare, welliver, wheelbarrow, wilber, wilbur, wolaver, wolber, wolfer, wolfrey, wolper, woolever