Pokemon that work best for being Sweepers are Pokemon with high Speed and high Attack for a Physical Sweeper, or high Special Attack for a Special Sweeper. Some Sweepers don't have the power or Speed to start off with so that's where Dragon Dance comes into play on Gyarados, Tyranitar, Dragonite, and Salamence. Special Sweepers sometimes setup Calm Mind so they can have more Special Attack and more Special Defence to sweep and be protected.