Piranha Plant's neutral attack consists of a jab with its leaf, then a leaf swipe, and either a headbutt or series of bites to finish off. The first hit comes out very fast at frame 2, making it effective for grounded combo breaking, quick punishes or out-framing many moves. The headbutt is useful for starting tech chases due to the Sakurai Angle and low endlag, while the bite attack is excellent for racking damage, typically dealing ~20% combined with the first 2 hits and held long enough just before it ends.
For the technical data of each individual hit, see: