Piranha Plant vs Jigglypuff

Jigglypuff is generally used as an aerial fighter, using your neutral B and up smash / up tilt makes it very difficult for a Jigglypuff to approach you.

Go to Final Destination and hold B. Jigglypuff can not get in and out before getting hit with the spike ball

Side B and you win every time. Thats how I got to 5768901 GSP