Overview
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Mew is an extremely versatile Pokemon because it can learn every TM and HM in the game. Furthermore, Mew is the only Defogger in the metagame with access to Will-O-Wisp and no Stealth Rock weakness, which lets it cripple Defiant users such as Bisharp by halving their Attack. Overall, Mew has good offensive and defensive stats but is not really that outstanding when compared to bulkier Psychic-types such as Mega Slowbro, regular Slowbro, and Cresselia. Mew has a good Speed stat as well, which lets it outspeed slower Pokemon and attack them. Mew also has access to a form of reliable recovery in Soft-Boiled, which contributes to Mew's longevity on the field. Mew has a usable ability in Synchronize, which can punish status users if they inflict status on Mew. It can also provide utility against Scald burns. However, Mew has a subpar Psychic typing, which leaves it very vulnerable against to common Bug-, Ghost-, and Dark-types, such as Scizor, Gengar, and Mega Gyarados, and Gengar. (matching order) Mew also has four-moveslot syndrome because it cannot benefit from all move options it learns. Despite Mew's incredibly huge movepool, there are only it only has a few viable sets that aren't outclassed by other Pokemon in the tier. (not a huge issue but you keep the "Mew is" "Mew has" sentence structure throughout this entire paragraph. it'd be nice to see some variation)
Stallbreaker
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name: Stallbreaker
move 1: Taunt
move 2: Soft-Boiled
move 3: Will-O-Wisp
move 4: Knock Off / Psychic
ability: Synchronize
item: Leftovers
evs: 252 HP / 224 SpD / 32 Spe
nature: Careful / Calm
Moves
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Taunt forces the foe to use damaging attacks and prevents them from boosting, setting up entry hazards, and recovering. Soft-Boiled provides reliable recovery for Mew, healing 50% of its health. Will-O-Wisp is another utility move which burns physical attackers and cripples them by halving their Attack. Knock Off prevents Mew from Struggling if it has been Taunted and additionally removes the foe's item. Psychic can be used in the fourth slot for a more powerful attack than Knock Off, (comma) as it is boosted by STAB and hits Pokemon such as Keldeo and Mega Lopunny for super effective damage, as well as Pokemon such as Clefable and Mega Venusaur, which is important, (comma) as they're two Pokemon Mew is supposed to beat. But, Ice Beam can also be used in the fourth slot to beat specially defensive Gliscor along with Landorus.
Set Details
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Synchronize statuses the opposing Pokemon if it statuses Mew, except if the foe is immune to that status. Leftovers provides passive recovery for Mew, boosting its longevity. The Speed investment lets Mew outspeed everything up to maximum Speed base 70s such as Jolly Bisharp and burn them before they can KO it. The HP EVs boost Mew's overall bulk while the Special Defense EVs give a boost to raise Mew's Special Defense stat, which is boosted even further by a Careful or Calm nature. Either a Careful or Calm nature should be ran - Use a Careful nature if running Knock Off is used, and, but use a Calm nature if running Night Shade (this is not slashed on the set) is used, because it reduces to reduce damage taken from Foul Play damage if used on Mew. A secondary spread can be used of 252 HP / 224 Def / 32 Spe can be used, as it lets Mew take on physical attackers better and avoid the 2HKO from Mega Lopunny's Return after Stealth Rock. A third spread of 252 HP / 148 SpD / 108 Spe is another option to outspeed Jolly Bisharp and Adamant Dragonite, but, with this spread, Mew has far less bulk.
Usage Tips
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Mew is best used on teams that struggle against stall, as it can come in on defensive Pokemon and use Taunt. Mew can spread burns against offensive physically oriented teams early-game and provide setup opportunities for teammates. Mew can be used as a tank, as it has good overall bulk, especially on the special side (if you can find a way to phrase this without saying "side" - because there are no sides - then you can keep that). Try to avoid getting statused, unless your team has cleric support. The activation of Synchronize isn't worth acquiring a status affliction for. Make sure to keep Mew as healthy as possible, as a defensive Pokemon may hit it on the switch and knock Mew out if it is at low HP. If you're unsure what to do, go for Knock Off, as most Pokemon will not appreciate having their item removed. When facing an opponent with Pursuit, the best thing to do is go for Will-O-Wisp, as all common Pursuit users are physical attackers. Watch out for Mega Sableye, as the best thing Mew can do against it is burn it with Synchronize, as it bounces all other status attacks back. However, if Mew will must be burned itself too if it wants to burn Mega Sableye.
Team Options
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Special attackers such as Mega Diancie and Raikou appreciate Mew beating specially defensive Pokemon such as Chansey and Ferrothorn one-on-one, and thus, they make for good partners. Setup sweepers such as Mega Charizard X, Mega Scizor, and Azumarill take advantage of Mew weakening physical attackers with burns, as they can use this to set up. Cleric support from Pokemon such as Chansey, Sylveon, and Clefable is appreciated to cure Mew from status. However, the former should only be used on defensive teams. Fighting-types such as Keldeo and Mega Lopunny are great partners for their ability to beat all Pursuit users themselves, and they have good synergy with Mew, as they resist Bug and Dark, and while Mew can switch into Psychic-type attacks for them. Other status absorbers such as Conkeldurr and Heatran are also good choices. The former can also beat common Pursuit users for Mew, (remove comma) and has relatively good synergy with it.
Defog
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name: Defog
move 1: Defog
move 2: Soft-Boiled
move 3: Will-O-Wisp / Taunt
move 4: Psychic / Knock Off
ability: Synchronize
item: Leftovers
evs: 252 HP / 224 SpD / 32 Spe
nature: Calm / Careful
Moves
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Defog removes entry hazards on both sides of the field, which can be useful for teammates that are weak to Stealth Rock or lack recovery. (space here) Soft-Boiled heals damage taken by 50% of Mew's HP and helps Mew stay healthy. Will-O-Wisp hampers physical attackers by burning them and also wears them slowly down slowly by inflicting some damage at the end of each turn. Taunt can be used in the third slot because it cripples defensive Pokemon by forcing them to attack, and it also prevents foes from setting up. Psychic prevents Mew from being Taunt bait and has good power with decent coverage against Pokemon such as Mega Venusaur. On this set, Psychic is a superior option to Knock Off, as this set does not include the combination of Taunt and Will-O-Wisp and therefore values the extra power more because of that, the extra power is better. Knock Off is another secondary option in the second slot (I think you mean fourth slot? according to the moveset) for its ability to remove items from foes if they are hit. Landorus and specially defensive Gliscor are punished by Ice Beam, which has decent power and good coverage, (remove comma) and thus is a usable option. Stealth Rock is a second option in the fourth slot, (there are already two options there - Psychic and Knock Off - so it's not a second option) as it hits damages foes each time as they switch in, but is somewhat counterproductive with Defog, which removes it.
Set Details
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Synchronize spreads status to foes that inflict status on Mew, as long as they are not immune to that status. Leftovers provides some passive recovery for Mew. The HP and Special Defense investment gives a boost to Mew's bulk and lets it avoid the 2HKO from Latios's Draco Meteor and Modest Landorus's Earth Power after Stealth Rock, and a Careful nature gives another boost to Mew's Special Defense. The Speed EVs let Mew outspeed and burn Pokemon such as Max maximum Speed Tyranitar and Adamant Bisharp. A Calm nature should be used alongside Psychic if Psychic is used, while a Careful nature should only be used if Mew is running Knock Off. A spread of 252 HP / 148 SpD / 108 Spe can be used to outspeed Max maximum Speed Jolly Bisharp as well as Max maximum Speed Jolly Breloom, but running it causes Mew to lose out on some bulk.
Usage Tips
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This set fits best on balanced or bulky offense teams, (remove comma) but doesn't fit on teams using entry hazards at all, as it functions as a hazard remover. Mew can switch into defensive Pokemon that set up entry hazards, Taunt them, and continue with Defogging the entry hazards away. Will-O-Wisp is Mew's primary option against physical attackers unless one of its teammates desperately needs its Defog support. Be careful with Defog if there is a Bisharp with Defiant on the opposing team - it can easily come in, (comma) and get an Attack boost, and Pursuit trap Mew after. Mew can be used to tank opposing attacks from foes, as it has good overall bulk and can recover back any damage taken.
Team Options
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Pokemon weak to Stealth Rock that appreciate Mew's Defog support, such as Mega Charizard Y, Mega Pinsir, and Talonflame, make for good partners. Setup sweepers such as Mega Charizard X, Scizor, and Dragonite, (remove comma) can use burned foes as a setup opportunity for themselves. Pokemon that struggle against defensive Pokemon, such as Raikou, are good choices because Mew can stallbreak for them. Cleric support from Clefable or Celebi is very nice because status will eventually wear Mew down. Fighting-types, (comma) such as Keldeo, Infernape, and Conkeldurr, are excellent partners for their ability to beat common Pursuit users. This set struggles against Fire-types, so teammates that can beat them one-on-one, such as Tyranitar and Gyarados, (space here) are good partners. This set is completely beaten by faster Taunt users, so Pokemon that can take the most common users such as Sableye on make good partners. If running Stealth Rock is ran, offensive Pokemon that take advantage of Stealth Rock to KO foes with more ease are good teammates.
Other Options
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A set with Baton Pass and either Swords Dance, Nasty Plot, or Rock Polish can be used to allow for teammates to sweep, but Scolipede does the former better and the latter is better done by Celebi does the second better (if Celebi also runs Rock Polish, you can say "does the latter two better") because of its superior defensive typing. An offensive set can be used on Mew for its to take advantage of Mew's huge coverage movepool, but Mew has low offensive stats compared to other Psychic-types such as Latios, which makes it unfit for this role. A lead set along the lines of Taunt, Stealth Rock, Tailwind, and Explosion is an option, (remove comma) but is better done by Azelf because of its better Speed and offenses. A Choice set with Trick can be used to prevent setup while delivering some offensive presence, but most targets from Trick are crippled by Taunt and Mew's offensive presence is somewhat lacking compared to other Psychic-types such as Latios. Earth Powerturns Mew into a lure as it can KO Heatran, which Mew lures in, but has no other specific targets and thus because of that, isn't worth a main slash. Seismic Toss and Night Shade can be used, (comma) as they hit foes for constant consistent damage, (remove comma) and hit Mega Pokemon harder, but Knock Off generally provides more utility. Thunder Wave is a utility move that cripples a lot of offensive Pokemon, (comma) as it lowers their Speed greatly, but Mew lacks the moveslot for it. Colbur Berry lets Mew take less damage from Knock Off and Pursuit, (comma) among other Dark-type moves, but the extra recovery of Leftovers is usually preferred. Transform is a final option that lets Mew transform into the opposing Pokemon and take an attack better by changing its typing, but this doesn't always work and takes up an important turn.
Checks & Counters
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**Pursuit Trappers**: Pursuit trappers, (comma) such as Tyranitar, Bisharp, and Weavile, can trap Mew and OHKO it with Pursuit. The latter outspeeds it, but they all hate to get burned. Additionally, Bisharp can switch into a Defog to boost its Attack by two stages because of Defiant.
**Faster Taunt Users**: Faster Taunt users such as Azelf and Prankster Taunt users such as Sableye and Whimsicott limit Mew to only one a single move and completely shut down its Defog set.
**Fire-types**: Fire-types such as Heatran, Mega Charizard X, Mega Charizard Y, and Talonflame are immune to burns and can beat Mew with their STAB attacks. Heatran's Fire-type attacks get a boost if it switches into Will-O-Wisp, thanks to Flash Fire.
**Status**: Toxic wears down Mew turn after turn, and burn steadily takes off damage as well. However, the users must be wary of Synchronize because it they may cripple themselves by inflicting the same status.
**Bug-types**: Bug-types such as Mega Scizor and Mega Beedrill can OHKO Mew with one of their STAB attacks after Stealth Rock damage (is that what you mean?) and Stealth Rock support. Both are crippled by burns, however.
**Dark-types**: Dark-types such as Bisharp, Tyranitar, and Mega Sableye can all take Mew's hits. Bisharp and Tyranitar hate Will-O-Wisp, however, though Mega Sableye cannot be Taunted or burned and can set up on Mew while taking next to nothing from Knock Off.
**Powerful Special Attackers**: Powerful special attackers such as Keldeo, Serperior, Dragalge, and Mega Charizard Y don't really get hampered by burns and can easily KO Mew with their STAB attacks. Substitute + Calm Mind Keldeo can set up as long as Mew does not run Psyshock if it is a Substitute + Calm Mind variant, while Charizard is immune to burns.
