From the Super Mario Wiki
Rising Uppercut is Little Mac's up special move appearing in Super Smash Bros. for Nintendo 3DS / Wii U. Little Mac leaps up into the air, spinning around and punching multiple times, dealing multiple hits to any opponents nearby, and ending with a more powerful punch to send them flying. This move hardly offers any horizontal movement, however, and its vertical travel distance is only about as good as an average jump if it's used in the air. Because of those flaws, Rising Uppercut is often considered to be the worst recovery move in the game.
Tornado Uppercut is the first custom variant of this move; it only deals one hit to opponents, and is weaker, but has greater vertical distance. The second is Rising Smash, which deals one blow to send opponents into the air, then a second more powerful punch the send them flying; the move does not have as much vertical distance, however.