Azumarill: Azu can enter on "every" move and kill but it has to be careful of Shield. Just Knock Off at can actually kill Aegislash even if it get the -2 Shield drop. Av Azumarill got high chances to be 3hko. It has more problems in takin off SubToxic set tho.
Still a good check.
Bisharp: It just have to be careful to Sacred Sword. It walls every other move and thanks to Defiant it doesn't give a single fuck of KShield, Knock Off still OHKOes it. It can trap it with Pursuit. Sucker Punch (if Adamant) helps vs max speed set, Jolly still outspeeds it. SubToxic is totally walled.
A check, sometimes a counter.
Breloom: It's definitely not a check, neither a counter. But it can Spore it (and Shield doesn't protect against status, another reason to not define KShield "op")
Chansey: It walls it, SSword is 3HKO after SR. The only problem is that Chansey can't do nothing to stop Aegislash. SD set wins, Mixed loses PPwar unless crits, SubToxic can waste Bell's PPs or force the switch but nothing more.
Counter? Surely more check that not.
Mega Charizard X: Offensive set is just a Revengekiller if it got EQ but can win anyway 50/50 KShield using FBlitz/Fire Punch on an Aegi that tries to stop the possible DDance. Bulky Dancer set takes big damages too, but it got more possibilities to win 50/50 thanks to Roost. SDefensive set can be 2HKOed only with SR up and kills with EQ.
SD set, missing the 2HKO w/ SSneak at Adamant +2 and being killed by every move in Blade Form.
It can check and sometimes "counter", revengekiller.
Mega Charizard Y: It can enter on a Shadow Ball and kill with Fire STAB (screw Blast miss) or Roosting on Shield; Char Y should win anyway the 1v1 being faster. SD set at Adamant +2 doesn't kill with SSneak and get killed.
Revengekiller and check w/out SR up.
Clefable: Mixed pivot set gotta run Iron Head to be dangerous, losing the priority or the important SSword. SBall fails the 2HKO if Clef still got lefties. Quiet Aegi is slower so Clefable can Wish or Calm Mind in front of the ghost, plus it can Protect to scout moveset. MagicGuard lols at SubToxic and kills w/fire move (or Stored Power/Moonblast in the long way). Also SD set gotta run Iron Head to be dangerous. Unaware Clefable does same things with the exception to 100% win the 1v1 with SubToxic unless it got Heal Bell.
Counter, at least check.
Conkeldurr: Its only good OU set is AVest that wins vs every Aegi's set (SubToxic is more dangerous, and Iron Head +2 Adamant miss the OHKO). Knock Off kills Aegi even with -2 drop, thanks to being slower, but using a fight move on Shield can bypass drop (worthy? I think not but w/e).
Counter, at least check.
Dragonite: It takes around 25-30% from SBall with Scale, and it outspeeds and kill with EQ if Band or it can dance so Aegi can't Shield without being punished.
Rkiller, check.
Excadrill: It can be killed by Mixed SBall + Sneak (Ssword does like 90%). It can just enter on SBall if AV and killing, but AV set is so rare. It can enter on SD set but SSword at +0 Adamant got high chances to OHKO. One positive note: EQ is always OHKO.
Not a check, just a revengekiller.
Ferrothorn: There's not a single move that can OHKO max def+ Ferrothorn, neither SSword at +2 Adamant (80%). It can Seed on Aegi bypassing Shield (just be careful with Sub set, but PWhip breaks the sub if it's in Blade Form). It can set up hazards on the ghost, not useful for its owner.
Check.
Garchomp: Mixed fails to KO w/SBall + Sneak and get killed by EQ in Blade form. 50/50 with SD or EQ on Shield still exists.
A sort of check and revengekiller.
Mega Garchomp: Like Garchomp but a bit bulkier.
Gliscor: It can enter on every move at full life and kills back with EQ or Subbing on Shield. It always wins vs SD set and have a good matchup vs SubToxic.
Check.
Greninja: It can enter on every move but SSword. Fails the OHKO on Shield Form with Dark Pulse.
It can revengekill.
/ Gyarados(Mega): Situation is strange. Gyara can enter on every Aegi's move, but does Gyara mega evolve or just attack or just dancin? Gyara got advantage but Aegi can win in some way.
"Check", it uses Aegi as statup fodder or just kills it.
Heatran: Heatran can enter on every move of mixed set, though SSword 2HKOes it w/SR up. Heatran outspeeds Aegi and kill, even though Aegi can survive to a Lava Plume if Shielded but it risks the burn. SD set OHKOes it w/SSword but it gonna pass through a Lava Plume too (and its burn rate). SubToxic is quite walled cuz SBall is a 4HKO on SDef Heatran.
Check, SubToxic "counter".
Hippowdon: this mon gotta run some SDef investment to win the 1v1 vs Aegi. Max SDef Hippo (lol?) takes around 40% and kills back w/EQ so it can be a sort of check yeah. SD set is completely walled, SubToxic can work around stalling it.
"Check".
Kyurem-B: This mon can enter basically on every move that's not Iron Head/Flash Cannon and win the 50/50 with sub + Earth power. Not that safe check but it got ways to win vs Aegi so why the fuck not. AV takes less than 40% by SBall, SD set can take an EP and kill w/SSword or Iron Head, SubToxic got a real bad matchup vs KyuB.
A sort of check.
Landorus-I: SBall does huge damage on Lando so it's not a safe check lol but it always OHKOes Aegi w/Earth Power. SD set loses the 1v1, SubToxic can Toxic/SBall under sub and KShield but it's forced to switch after this.
Revengekiller
Landorus-T: Lando-T is easily 2HKOed by SBall but it can kill back with EQ obviously. The only problem is that Aegi can survive to one EQ if shielded and kill with SBall+SSneak in this scenario. SD Set is completely walled and SubToxic can win in some way.
Bad Check.
Mamoswine: Mamo get killed by SBall + SSneak (or just Iron Head), it can just have chances to OHKO Shield form with LO.
Sort of revengekiller.
Mandibuzz: Mandi is one of the best counter of Mixed and SD set (with the exception of Head Smash lol but it's p rare man u gotta be cteammed to get that done). Fast version w/Taunt can enter on SubToxic set even if it risks to get a Toxic on switch-in. Fplay always breaks sub.
Counter.
Mega Mawile: It can enter on SBall and win 50/50 by SD on KShield and Sucker Punch back (also SPunch avoids -2drop) or Fire Fang at least. +2 Sucker Punch OHKOes Shield form. SubToxic got a better matchup vs MegaMawile due to the fact it can sub on SuckerPunch.
A bad check, but it can revengekill.
Mega Pinsir: not a check tho, but Aegi gotta be careful cuz +2 EQ kills shield form so it can be rkilled so ez by Pinsir that can enter on Blade form and Dance on Shield or just EQ and kill it.
A sort of revengekiller
Quagsire: 2HKOed by Mixed's SBall, it can't do pretty much also vs SubToxic but it can take one SBall and kill back w/EQ due to the fact it's slower than Aegi. Thanks to Unaware, it completely walls SD set.
SD set's counter, not a check of other sets.
Rotom-W: 2HKOed by Mixed's SBall, it can just burn Aegi but it's not so useful for mixed and subtoxic set. It walls SD set.
SD set's counter, a bad Mixed set check if full SDefensive (>SDef Rotom-W in XY OU).
/ Scizor(mega): CBZor is 2HKOed by SBall and Aegi can also shield on every move and drop the bug. Mega Scizor is bulkier so it's 2HKOed just w/SR up but it can roost and kill back w/Knock Off. It can also Roost/SD on KShield so there's the 50/50 fact.
MegaScizor can check Aegi.
Sylveon: Aegi gotta run Iron Head to be dangerous, SBall misses the 4HKO. Wish Protect can scout Aegi's moveset, Heal Bell allows Sylveon to don't lose 1v1 vs SubToxic (plus Hyper Voice hits under sub). It loses 1v1 vs SD set.
It's a mixed/subtoxic counter.
Terrakion: Aegi walls its STABS but it can SD + EQ (high chances to OHKO w/out LO on Shield form), usual 50/50 condition that makes it a
sort of rkiller. (even if Aegi is a reason why Terrakion is not so used)
Thundurus-I: we gotta be grateful to Aegi if this thing got a check in offense teams. Thundurus is killed by SBall+SSneak. Thundurus itself goes close to 2hko w/LO Tbolt, Aegi is one of the few mons that are not at least 2HKOed by its neutral STAB (and that can do something back). Aegi's ban will result in a loss of one of its most important checks.
EDIT: Defiant set can win the 1v1 vs Aegi thx to KnockOff
Togekiss: it's walled by Aegi (with exception of Fire move ok), but Aegi itself can't do much without Steel STAB.
/ Tyranitar(mega): BulkyTar is killed by SSword (unless Chople berry but it misses OHKO on Aegi because it's faster). Mega Tyranitar can dance on KShield and kill w/Crunch or EQ. SSword doesnt OHKO Mega Tyranitar. TTar can always enter on SBall and try to pursuit but it gotta be careful by KShield.
Check,
it uses Aegi as setup fodder if mega or just kills it.
Vaporeon: Vaporeon is 3HKOed by SBall, it can Wish+Protect and attack w/Scald. +2 SD Aegi set can just 2HKO w/SSword but it can be burned by Scald so it's not worthy yeah. SubToxic can win 1v1 due to the fact Vaporeon doesn't break sub with a single Scald.
Check.
Mega Venusaur: MegaVenu can be 3HKOed by SBall and +2 SSneak and it can do several damages w/EQ or at least HP Fire. It can also Sleep Powder or Seed on Aegislash. Venusaur also doesn't fear SubToxic set.
Something similar to a counter.
Zapdos: Defensive set is 2HKOed by SBall, SDefensive got 3HKOed by it. It can do several damages w/Heat Wave or just spam TBolt + Roost if SDefensive. Both sets can threat SD set and sub is always broken by just TBolt.
Check/Counter.
Other tiers' mon that can do something vs Aegi:
(It enters on every move bar SSword and OHKOes Shield Form w/EQ. Only Balloon Aegi totally walls it if it ain't got WCharge or U-Turn)
(SDefensive is 3HKOed by SBall and Foul Play does damage. Immune to Toxic)
(AV set is 3HKOed by SBall and it does damage w/Knock Off - Regenerator helps)
(3HKOed by SBall, EQ OHKOes Blade form and does huge damage to Shield)
(3HKOed by SBall, Restalker wins 1v1)
(3HKOed by SBall, Dark Pulse 2HKOes Shield Form)
(It can enter on special moves but SSword can 2HKO it)
(Its ability let it wall entirely Aegislash bar Flash Cannon or Toxic. It can seed it bypassing Shield)
(I laughed but lookin at calcs, it checks Aegi and kills it)
(Take an hit and kill back. Sacred Fire doesn't get drop by KS; AV Entei is 3hkoed by every Aegi's move, CB Sacred Fire OHKOes Shield form)
(It walls Aegi bar Iron Head)
(SDef is 3hkoed and kills back w/EPower or EQ. It also got Recover)
(Ssword doesn't OHKO and it kills back with stabs, though missing OHKO on Shield Form with every move)
(Good check, Specs Dark Pulse is very close to OHKO Aegi's Shield form)
(Checks SBall and trap Aegi or KO it with stabs; it gotta be careful to shield tho)
(3HKOed by SBall, it can recover on Aegi and do several damage with Scald and maybe burn it)
(3HKOed by SSword, it can win 1v1 thanks to Recover. It loses to SD set but w/e)
(Defensive is 3HKOed by SSword and it's so close to OHKO w/EQ)
(SDef get 3HKOed and kills back w/EQ or Knock Off)
(3HKOed by SBall, it CM/Rests on Aegi and win 1v1)
(SSword 3HKOes w/lefties recovery, Wish+Protect+Foul play let it win 1v1)
(Yeah this AV thing takes hits and kills back w/Drill Run or Knock Off)
(It walls Aegi bar SSword/Iron Head and does good damages w/SBall)
(It can wall Aegi, Spore it and break its sub or do big damage on it w/Foul Play)