The general consensus would be Tapu Lele. Psychic Terrain boosted STAB Psychic and Psyshock combined with 130 base SpA hit ridiculously hard, with Psyshock getting Chansey, while Moonblast gets good coverage alongside it. It also sits in a solid speed tier so it can make use of it's power. Additionally, Psychic Terrain prevents it from getting killed by Bullet Punch or other priority. There are very few reliable switch-ins to a Choice Specs set, and a Scarf turns it into a excellent revenge killer and late-game cleaner. All the other Tapus are really good mons as well, but Lele pretty clearly stands a bit ahead.