Ladies and gents, I believe I have found the perfect Talonflame counter.
Meet
Zapdos:
A force to be reckoned with since its inception. It was solid OU for 4 gens, top UU last gen, and now it gets legal Lightningrod to play with.
Calcs (think I did them correctly)
Talonflame vs. Zapdos
252+ Atk Flying Gem (custom) Acrobatics (110 BP) vs. 248 HP / 236+ Def Zapdos: 87-103 (22.71 - 26.89%) --
possible 5HKO
252+ Atk Life Orb (custom) Brave Bird vs. 248 HP / 236+ Def Zapdos: 82-97 (21.4 - 25.32%) --
possible 5HKO
252+ Atk (custom) Flare Blitz vs. 248 HP / 236+ Def Zapdos: 127-151 (33.15 - 39.42%) --
guaranteed 3HKO after Stealth Rock
Zapdos vs. Talonflame
0 SpA Zapdos Thunderbolt vs. 0 HP / 0 SpD (custom): 338-398 (113.8 - 134%) --
guaranteed OHKO
0 SpA Zapdos AncientPower vs. 0 HP / 0 SpD (custom): 284-336 (95.62 - 113.13%) --
guaranteed 2HKO
0 SpA Zapdos Discharge vs. 0 HP / 0 SpD Gliscor: 284-336 (95.62 - 113.13%) --
68.75% chance to OHKO
Zapdos can switch into any attack, take 2 hits (even with SR up), and OHKO Talonflame right back. If that's not a counter I don't know what is.
Discharge and AncientPower (useless, but dat 10% chance of all stats boost) fall just shy of a KO- with just 60 SpA EVs a OHKO for both is guaranteed. If you do that, Acrobatics still can't 4HKO.
So yeah, anyone else thinking this electric bird could rise to OU again?
EDIT: Didn't account for nerfed Thunderbolt. Still KOes though. 107.74 - 127.27% with no investment whatsoever at 90 BP.