Petilil

It's hard to find much use for Petilil in the Little Cup metagame. It's slow and not very bulky, and aside from access to Sleep Powder and niche options like Healing Wish is completely outclassed by fellow offensive Grass-type Snivy, which has a great ability in Contrary, much better Speed, and nice utility moves like Defog and Knock Off. The closest thing Petilil has to a niche is that of a self-setting sun sweeper due to the power of Solar Beam coupled with a good Special Attack stat, but such a niche is rather subpar seeing as setting up Sunny Day leaves Petilil vulnerable for a whole turn, which is especially bad for a Pokemon with the aforementioned issues of poor bulk and Speed. Even in this role, it's outclassed by Bulbasaur, Bellsprout, and even Oddish, which have better typings that make setting up easier, in addition to better bulk, power, Speed, or coverage.