Talonflame (rr heck, Bisharp and Mega Gyarados for Psychics). But hey I'm guessing that after people realize that a Aegislash will do nil for the viability of these pokemons, the Smogon Berd will be next in line.
Difference between Talonflame and Aegislash is that, for one, Aegislash doesn't have much of an issue switching in to psychics and some fighting types (okay not most of them, pretty much just Mega Medicham.) Talonflame is really frail, I'm not even going to run calcs but I'm pretty sure it's OHKOed by Lati@s' Draco Meteor, takes a ton from Mega Garde's Psyshock and same with Alakazam. Slowbro counters Talonflame, actually. And Mega Medicham nearly OHKOs Talonflame with resisted HJK and OHKOs with Zen Headbutt, while Mega Heracross OHKOs with Rock Blast so it has trouble switching in to that too. Oh, and Bisharp and Mega Dos eat it with Focus Blast.
Talonflame is a revenge killer only. That's all it basically does. It also has a number of things that reliably counter it. Aegislash is a counter to those mons.
But people need to stop using "it'll make X more viable," and people need to stop nitpicking those arguments (no one with a straight face would seriously fucking say "ban Talonflame it can RK Medicham," there are other issues with Aegislash that Talon doesn't have,) cause:
A. Both of Latias and Latios have very solid usage (especially when you consider that they're the same pokemon with slight differences) despite having almost zero capacity to not get screwed by Aegislash. This shows that good Psychics with exceptional qualities can be good in OU, even if they're hard countered/pursuit trapped by Aegislash.
B. Hawlucha is shit and won't be good with Aegislash gone. It has a large number of problems, namely low bulk and not enough power to break through many commons members of stall teams.
C. Mega Heracross has both of Earthquake and Knock Off
D. Why is it bad that Mega Garde and Cham have a reliable counter? Cause both of them are OU and get respectable usage anyway, it's not like they're being rendered totally unviable by Aegislash.
Both are utterly insane when you think about it. Garde has
one, singular good counter in Aegislash. Mega Scizor can counter but it hates burns a lot more than Aegislash. Everything else is a check at best; if they try to switch in to Psyshock/Focus Blast/WAIL OF THE BANSHEE they lose. Even Chansey needs to be at really high health to switch in to Psyshock, and it outright loses to any set that has Calm Mind or Taunt.
Cham is a bit less ridiculous cause it has reliable counters in bulky Psychics/Ghosts not weak to whatever elemental punches it usually carries (Slowbro, Mew, Cresselia, Sableye is pretty much it) but it's still pretty ridiculous cause it just 2HKOs or just OHKOs anything that doesn't resist HJK, has STAB Zen Headbutt to deal with things that usually wall fighting types (Poison and Fairy types) and then elemental punches to fill in the gaps. Even Mew needs a bit of Def investment to avoid a 2HKO after SR. It just hits hard as shit.
Aegislash is the only mon that reliably counters Garde and the best way of handling Cham. Why do you think Bisharp is a top partner for both of them? Cause any defensive team relying on Aegislash to take care of them is screwed if it gets pursuit trapped. I know, I know, "don't check broken shit with broken shit" but I'm not convinced any of Aegis/Cham/Garde are broken. Point is that getting rid of a counter to Cham/Garde, while making them more viable (as it would with
any pokemon if you remove a prominent counter,) is not necessarily a good thing, cause both are stronk as living hell and are completely usable in OU.
Also can people stop pointing out obvious shit like "well but it's weak to erfquake."