My understanding is that Tapu Lele is supposed to wallbreaker. Therefore, if it has to be revenge killed to be dealt with, that means it's already done its job. Also, good luck revenge killing Specs Lele without a Dark type coming in on its Psychic STAB it's locked itself into. No priority renders that iffy speed stat kind of a moot point, especially if running a Scarf set. Not to mention, E Belt, Mind Plate, etc sets could theoretically bluff a Choice item, lure that Dark type in, and wipe it out with Moonblast.
Certainly not to say this thing is broken. I don't think a ban is in order, but this thing is going to be a defining force in the meta at the very least.
95 Speed narrows the range of things that can kill it even if it does not have Scarf. It seems to be like Hoopa-Unbound with a better speed tier, better defensive typing, and protection from priority. While Hoopa-Unbound and Tapu Lele do not have many counters, Lele's high enough speed, decent bulk, and immunity from priority make it more difficult to check.
Magaerna, Muk Alola, Mega-Metagross, Genesect, Celesteela, Skarmory, and Heatran are the only good checks that come to my mind. (I assume that Lele has Hidden Power Fire and not Thunderbolt.) In the case of Heatran, a psychic attack could pop its balloon, leaving it vulnerable to the ground-type Pokemon that the Lele user would likely have to deal with steel types.
Choice Band Scizor seemed to be the gold standard for being anti-(pure)fairy since it has additional utility as being a U-Turner if it is not running the Swords Dance set. Scizor would have the dubious distinction of being a steel type that cannot check Lele since it couldn't use its bullet punch.
I really feel that Lele and Koko make Genesect an important part of the meta. Scarf Iron Head becomes Bullet Punch.
If I were to speculate about the decision making process of the OU Council, I think this think Genesect isn't
quick banned because it provide a way for offensive teams to check this thing (but not counter it). Defensive teams can rely on some steel type. Scizor somewhat checks Koko if it has a low enough HP, but it is not a good check for Lele if it is not choice locked.
I don't think Genesect deserves to be quick-banned even though it is a fairly popular sentiment.
Offensive unevolved Scizor takes a chunk from Lele's Psychic.
252 SpA Tapu Lele Psychic vs. 248 HP / 0 SpD Scizor: 133-157 (38.7 - 45.7%) -- 16.4% chance to 2HKO after Stealth Rock
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Here is a comparison for Scarf Lele versus wall-breaking Hoopa-Unbound (with Life Orb), Kingdra (with Specs under Rain), and Serperior.
(With Terrain)
252 SpA Tapu Lele Psychic vs. 252 HP / 0 SpD Regigigas: 205-243 (48.3 - 57.3%) -- 45.3% chance to 2HKO after Leftovers recovery
252 SpA Tapu Lele Psyshock vs. 252 HP / 4 Def Regigigas: 180-213 (42.4 - 50.2%) -- guaranteed 3HKO after Leftovers recovery
(With Terrain + Life Orb)
252 SpA Life Orb Tapu Lele Psychic vs. 252 HP / 0 SpD Regigigas: 266-316 (62.7 - 74.5%) -- guaranteed 2HKO after Leftovers recovery
252 SpA Life Orb Tapu Lele Psyshock vs. 252 HP / 4 Def Regigigas: 234-277 (55.1 - 65.3%) -- guaranteed 2HKO after Leftovers recovery
252+ SpA Life Orb Hoopa-Unbound Psychic vs. 252 HP / 0 SpD Regigigas: 238-281 (56.1 - 66.2%) -- guaranteed 2HKO after Leftovers recovery
252+ SpA Life Orb Hoopa-Unbound Psyshock vs. 252 HP / 4 Def Regigigas: 211-250 (49.7 - 58.9%) -- 71.1% chance to 2HKO after Leftovers recovery
252+ SpA Life Orb Hoopa-Unbound Dark Pulse vs. 252 HP / 0 SpD Regigigas: 211-250 (49.7 - 58.9%) -- 71.1% chance to 2HKO after Leftovers recovery
(Under rain)
252+ SpA Choice Specs Kingdra Hydro Pump vs. 252 HP / 0 SpD Regigigas: 330-388 (77.8 - 91.5%) -- guaranteed 2HKO after Leftovers recovery
252+ SpA Choice Specs Kingdra Surf vs. 252 HP / 0 SpD Regigigas: 271-319 (63.9 - 75.2%) -- guaranteed 2HKO after Leftovers recovery
+2 252 SpA Serperior Leaf Storm vs. 252 HP / 0 SpD Regigigas: 271-321 (63.9 - 75.7%) -- guaranteed 2HKO after Leftovers recovery
As for Kingdra, it relies on another Pokemon otherwise it would be too slow and lack power, while Lele just needs its ability.
Serperior is vulnerable to priority, except Aqua Jet, and Priority Brave Bird was a thing last generation. Also, Grass is arguably less spamable than psychic. Serperior also needs to successfully use Leaf Storm in order to be that powerful.
As for its Special Bulk
252 SpA Choice Specs Keldeo Hydro Pump vs. 0 HP / 0 SpD Tapu Lele: 237-280 (84.3 - 99.6%) -- guaranteed 2HKO
252+ SpA Choice Specs Volcanion Steam Eruption vs. 0 HP / 0 SpD Tapu Lele: 262-310 (93.2 - 110.3%) -- 62.5% chance to OHKO
252+ SpA Choice Specs Volcanion Flamethrower vs. 0 HP / 0 SpD Tapu Lele: 214-253 (76.1 - 90%) -- guaranteed 2HKO
252+ SpA Choice Specs Volcanion Sludge Bomb vs. 0 HP / 0 SpD Tapu Lele: 286-338 (101.7 - 120.2%) -- guaranteed OHKO
252 SpA Heatran Flash Cannon vs. 0 HP / 0 SpD Tapu Lele: 234-276 (83.2 - 98.2%) -- guaranteed 2HKO
252+ SpA Volcanion Sludge Bomb vs. 0 HP / 0 SpD Tapu Lele: 192-226 (68.3 - 80.4%) -- guaranteed 2HKO
versus
252 SpA Tapu Lele Psychic vs. 4 HP / 0 SpD Volcanion: 241-285 (79.8 - 94.3%) -- guaranteed OHKO after Stealth Rock
252 SpA Life Orb Tapu Lele Psychic vs. 4 HP / 0 SpD Volcanion: 313-370 (103.6 - 122.5%) -- guaranteed OHKO
So, one needs a Pokemon with a high base special, STAB, a choice item, and highly-powered inaccurate move (although Volcanion's Steam Eruption isn't inaccurate) to kill it. Volcanion cannot outspeed Lele, unless Volcanion is running a Scarf while Lele isn't. Stab fully invested neutral moves could take it down, but it a coverage move doesn't have the power to so.
Physical Bulk:
252 Atk Landorus-Therian Earthquake vs. 0 HP / 0 Def Tapu Lele: 225-265 (80 - 94.3%) -- guaranteed 2HKO
252+ Atk Conkeldurr Poison Jab vs. 0 HP / 0 Def Tapu Lele: 258-304 (91.8 - 108.1%) -- 50% chance to OHKO
252 Atk Garchomp Poison Jab vs. 0 HP / 0 Def Tapu Lele: 222-262 (79 - 93.2%) -- guaranteed 2HKO
A fully invested, STAB high-powered attack cannot knock it out. Conkeldurr and Landorus-Therian have high base attack while Garchomp is slightly lower. A Scarf coverage move is not enough to kill it.
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