Victreebel

Victreebel rarely had a chance to shine in previous generations, having few options to give it any niche. That changes in BW RU, where Victreebel becomes one of the most threatening Pokemon in the game with the proper support. Its great 105 / 100 mixed attacking stats, along with its very powerful offensive moves, make Victreebel a solid Pokemon. But that's not all—under Sunny Day, Victreebel becomes a monster; Chlorophyll doubles its Speed, while Growth does the same to its offenses. Sun makes or breaks Victreebel; under sun it is ridiculously powerful, 2HKOing the entire tier, but outside of it, Victreebel is all but dead weight.

All this power comes at a price, however. Its poor defensive stats mean that even though it can decimate most of the tier in one or two hits, it will only be able to take one attack at best; priority also causes it huge problems defensively. Victreebel also has very limited offensive options, the lack of physical coverage practically requires it to go mixed. Although Victreebel has received very few changes since DPP, it is still capable of obliterating teams with some support.