>>46270540>>46270552Garchomp.
This is thanks to multiple factors, such as an insanely good movepool, fantastic stabs, great boosting moves, very good bulk, a speed stat that's just high enough to outpace the average, and an attack stat to let it hit like a truck. Rough Skin isn't a god-tier ability but it helps to punish u-turn spam and is nice on something that can take a good amount of hits. Garchomp also has few weaknesses and can easily stomp the things it's weak too. Fairy did little to hinder it. It's also surprisingly versatile, with numerous sets ranging from standard sweepers and wallbreakers to mixed attackers and even suicide leads or utility (with Rocky Helmet). With Gen 8, it's only gotten even stronger, as it can run Swords Dance with Scale Shot to compress it's boosting moves and avert 4MSS as well as shred substitutes and get around focus sashes. Even with the addition of the fairy type, it didn't hinder Chomp too much. Whether you like or hate Garchomp, you cannot deny it's power and wide variety of uses.
I can also say, having played National Dex OU quite a lot, that when Garchomp has access to Scale Shot and the toys of prior gens, it gets even better.
Do you want to know what power looks like? It's Mega Garchomp with Scale Shot and Swords Dance. That move alone turned the Mega into a force to be reckoned with.