Tangrowth

Tangrowth is undisputedly a great Pokemon in UU; it has high HP, good overall defensive stats, and useful offensive stats both physically and specially. On top of that, Tangrowth is one of the few Pokemon that get STAB on Power Whip. It has access to Sleep Powder, Stun Spore, Knock Off, and a great physical and special movepool as well. However, Tangrowth is in an unfortunate position in UU, where its best counters are also the top Pokemon in the tier; Venusaur and Blaziken, among others, can beat it easily one-on-one. The threat from special sweepers in UU is, in general, much greater than that from physical sweepers, and the physical sweepers that are still considered threats can often beat Tangrowth anyway.

Don't let this make you feel that Tangrowth is any the worse for wear, though. Tangrowth can still function as a bulky Grass-type and be an annoyance to the opponent thanks to Knock Off, Stun Spore, and Sleep Powder. All the Pokemon listed above hate having these moves used against them. Stealth Rock support makes Tangrowth even better on the field, as many of Tangrowth's counters hate having 25% of their HP chipped off. Tangrowth's potential is such that it can stand its ground with Power Whip and its support moves alone. It also is one of the best Rhyperior checks in the game and one of the only Pokemon in UU that can call a halt to Swords Dance Kabutops in the rain.