Roserade

At a glance, it looks like there is almost no reason to use Roserade in VGC. Amoonguss and Venusaur are both Grass / Poison types that not only see much more use in VGC, but also have a lot of positive traits over Roserade. Amoonguss boasts much greater bulk, a 100% accurate sleep move in Spore, and Rage Powder to redirect moves; Venusaur has increased Speed in sun thanks to Chlorophyll and a bulky Mega evolution to take hits more easily. However, Roserade has plenty of advantages over these two. Firstly, Roserade has a Special Attack stat of 125, meaning it hits harder than both Amoonguss and Venusaur. It also has 90 Speed, allowing it to outspeed Pokemon such as Rotom-H, Gardevoir, and Chandelure and put them to sleep before they can attack. Its ability, Technician, gives a boost to Hidden Power, giving it a powerful 90 Base Power Hidden Power Fire to hit Steel-types. It also deals with Pokemon such as Rotom-W, Azumarill, and Politoed very well. However, Roserade does have quite a few flaws. While it isn't necessarily slow, it's not very fast either, and is still outsped by Pokemon such as Charizard, Salamence, and Mega Kangaskhan. It also has quite poor physical bulk, meaning it has trouble taking physical attacks. Lastly, Roserade does have slight four-moveslot syndrome, as it really wants to run Magical Leaf, Sludge Bomb, Hidden Power Fire, Sleep Powder, and Protect all on the same set.