What strikes me with Mimikyu is how differently you have to deal with it than with other setup sweepers, mainly because it can always only get 2HKO'd in the best case scenario. This means that you can't just sacrifice something and revenge kill it w/ a faster mon, you either have to be able to wall it, or to let a mon die to it after breaking its disguise before being able to revenge kill it.



First, let's take a look at its setup opportunities. Thanks to its amazing ability, it can force out faster mons that can ohko it like Terrakion or Latias at +1 since they'll just break its disguise and get killed by play rough into shadow sneak, so if the mon in question is necessary, they'll obviously want to switch it out so Mimikyu can create itself setup scenarios like that. Moreover, it gets a free setup in front of slower mons that are able to take a neutral hit but not one at +2 (especially not a Never-Ending Nightmare) like Specs Primarina, Altaria-Mega or Nidoking and then something has to take the +2 Never-Ending Nightmare. However, only a few mons are able to leave that hit, most of which Mimikyu can get around with. There are two different types of scenarios that leave to the situation in the upcoming calcs : one where a mon is scared out by Mimikyu and switches out while it sets up and another one where Mimikyu sets up against a slower mon that is only threatened by a boosted attack so it breaks Mimikyu's disguise before switching out.



+2 252 Atk Mimikyu Never-Ending Nightmare (140 BP) vs. 252 HP / 176+ Def Amoonguss: 348-409 (80.5 - 94.6%) -- 12.5% chance to OHKO after Stealth Rock and Leftovers recovery (w/ Rocky Helmet or just Amoonguss switching into the attack it's a 50% chance) and it's also important to note that even if Amoonguss leaves it's still gonna be at a very low range which could let Mimikyu setup again on the switch.



+2 252 Atk Mimikyu Never-Ending Nightmare (140 BP) vs. 252 HP / 4 Def Aggron-Mega: 169-201 (49.1 - 58.4%) Aggron takes it pretty well and is able to threaten it back with an OHKO if the disguise is broken. Aggron-mega often gets chipped but not that much.

+2 252 Atk Mimikyu Shadow Claw vs. 252 HP / 4 Def Aggron-Mega: 85-102 (24.7 - 29.6%) However Mimikyu is able to fire off a second attack. Two low rolls means Aggron takes at least 73.8% which is a range it can be rather easily chipped to . And even if the Aggron isn't at the given range, it will be left at a very low range which can benefit another setup sweeper like Scizor, Altaria-mega or Latias.

For Steelix-mega it's kind of the same, just that it takes 71.7% min from the two moves used consecutively.



It's also important to note that Shadow Claw has a 12.5% critical rate which can leave Aggron and Steelix at an even lower range.



+2 252 Atk Mimikyu Never-Ending Nightmare (140 BP) vs. 252 HP / 156+ Def Eviolite Gligar: 178-211 (53.2 - 63.1%) -- guaranteed 2HKO

Gligar can easily eat a +2 Z-move however it doesn't have a move that can KO back and even worse :

0 Atk Gligar Earthquake vs. 4 HP / 0 Def Mimikyu: 102-121 (40.4 - 48%) -- guaranteed 3HKO

This means if Gligar switches in on a Mimikyu clicking SD, it won't be able to stop it from clicking another SD. And if it switches on a +2 Z-Move (which would mean the disguise got broken), the Mimikyu can SD on a turn Gligar uses Roost, the only problem being that the opponent can predict the SD and switch on a faster mon that takes a +4 Shadow Sneak but it's a hard one to pull since Mimikyu doesn't lose much by hitting two or three play rough / shadow claw before setting up up to +4.

+4 252 Atk Mimikyu Play Rough vs. 252 HP / 156+ Def Eviolite Gligar: 172-204 (51.4 - 61%) -- guaranteed 2HKO

However, it is important to note that Gligar can also run U-Turn, over Toxic so it can switch on Mimikyu, eat the +2 Never Ending Nightmare and then click U-Turn to break the disguise and bring a faster mon in that can sponge the +2 Shadow Sneak. It still leaves the Gligar at 47% max which can once again benefit another setup sweeper.



+2 252 Atk Mimikyu Never-Ending Nightmare (140 BP) vs. 252 HP / 80+ Def Hippowdon: 262-309 (62.3 - 73.5%)

+2 252 Atk Mimikyu Play Rough vs. 252 HP / 80+ Def Hippowdon: 169-199 (40.2 - 47.3%)

The combination of the two moves gets rid of Hippowdon most of the time and Hippowdown and even if it doesn't, Hippowdon doesn't do enough damage in return :

0 Atk Hippowdon Earthquake vs. 4 HP / 0 Def Mimikyu: 144-169 (57.1 - 67%)

Which means Mimikyu sets up again and 2HKOs at +4



And then obviously the king himself :

252 Atk Mimikyu Never-Ending Nightmare (140 BP) vs. 252 HP / 252+ Def Quagsire: 144-169 (36.5 - 42.8%) -- 97.8% chance to 3HKO after Leftovers recovery

Mimikyu gets completely walled by Quagsire, there's not much it can do about it outside of running Wood Hammer instead of Shadow Sneak but it feels like a really bad trade to me so I don't think it's a relevant set.



The player facing Mimikyu can obviously predict the Ghostium-Z and switch into his dark / normal type but most dark types aren't able to KO from full it while Play Rough does and Blissey is the only relevant normal type in the tier and is obviously not able to stop Mimikyu from setting up again.



We've now seen that Mimikyu doesn't struggle too much to find itself in a position where it can setup and that outside of U-Turn Gligar and Mega Steelix/Aggron no pokemon is able to take a +2 Never-Ending Nightmare and to deal with Mimikyu after it and even those 3 are left at a low amount of hp in exchange. So it basically picks up a free kill whenever it gets the opportunity to click sd. However, it's most likely the only kill it'll get in the match. Ironically, Mimikyu OHKO's almost nothing without a boost. So whatever Mimikyu sets up against, it will be able to break the disguise relatively safely which means Mimikyu becomes vulnerable to Scizor and most faster mons outside of Celebi, Latias, Gengar and Hydreigon (since scarf Dark Pulse doesn't do much) since +2 Shadow Sneak hits like wet bread :



+2 252 Atk Mimikyu Shadow Sneak vs. 0 HP / 4 Def Aerodactyl-Mega: 117-138 (38.8 - 45.8%) -- guaranteed 3HKO

+2 252 Atk Mimikyu Shadow Sneak vs. 164 HP / 0 Def Scizor: 102-121 (31.6 - 37.5%) -- 89.9% chance to 3HKO

+2 252 Atk Mimikyu Shadow Sneak vs. 0 HP / 4 Def Terrakion: 111-132 (34.3 - 40.8%) -- guaranteed 3HKO

+2 252 Atk Mimikyu Shadow Sneak vs. 0 HP / 4 Def Infernape: 135-159 (46 - 54.2%) -- 47.7% chance to 2HKO

+2 252 Atk Mimikyu Shadow Sneak vs. 0 HP / 0 Def Cobalion: 82-97 (25.3 - 30%) -- guaranteed 4HKO



The only way it can keep its Disguise and still get a kill is if it predicts a switch and then there are none of the 6 mons I previously stated on the opposing team, which typically happens in the match-up against Offense. So for exemple you bring Mimikyu on a Scarf Krook which is the only way for the opponent to revenge kill [redacted] so they're kind of forced to switch out which allows you to click SD and claim one and you still have your disguise so you can pull it off another time or preserve it to prevent a sweep. It should be noted that Mimikyu can still be useful with its decent special defense, speed and priority even after the the disguise is broken, though it loses a lot of viability.



Thus, instead of being able to sweep through teams like other top threats in UU, Mimikyu will very easily get a kill or a lot of damage on Gligar / Steelix / Aggron at any time in the game which can enable a path for another setup sweeper while being able to revenge kill threats like a +1 Altaria or a +1 Latias if needed. However, there are 3 downsides to this strategy. The player facing Mimikyu can often sacrifice pretty much any mon he doesn't need after breaking the disguise, the player using Mimikyu will have to chose carefully between keeping Mimikyu to avoid getting swept and getting rid of Mimikyu after destroying something with a +2 attack, and building with Mimikyu seems in general to be kind of tricky as it neither provide reliable defensive utility nor reliable offensive utility, it just kind of self destructs.



This is how I feel Mimikyu to be the best at, if well played it can go on a rampage against more offensive teams whereas it will have trouble keeping its disguise against bulkier builds but will effectively discourage setup sweepers in any case as long as the disguise isn't broken. Which is why I believe it to not be broken and to instead reward clever plays and teambuilding skills.