SM OU My second OU team with Mew in it

[Mew Primigenio]

Mew Primigenio (Mew) @ Mewnium Z
Ability: Synchronize
Shiny: Yes
EVs: 4 HP / 252 SpA / 252 Spe
Timid Nature
IVs: 0 Atk
- Nasty Plot
- Psychic
- Aura Sphere
- Soft-Boiled
Mew has a role of special sweeper, a timid nature to have a better speed, and to be able to carry soft-boiled instead of rock polish, nasty plot to get more SpA because it is a special sweeper, psychic to use the Z move genesis supernova, and a STAB move, and aura sphere for steel and dark pokemon that can resist or be inmune to Mew's attacks.

Tapu Koko @ Light Clay
Ability: Electric Surge
EVs: 248 HP / 8 Atk / 252 Spe
Jolly Nature
- Taunt
- Reflect
- Light Screen
- U-turn
Tapu Koko's role is to put reflect and light screen, that can help mew to have a better bulk, because it only has 4 evs in HP, and 0 in both of its defenses, with the light clay to extend their duration, and U-turn for predictions and also to help with dark pokemon that are inmune to Mew's attacks, with EVS for bulk and speed.

Ferrothorn @ Leftovers
Ability: Iron Barbs
EVs: 252 HP / 24 Def / 232 SpD
Careful Nature
IVs: 0 Spe
- Spikes
- Leech Seed
- Thunder Wave
- Power Whip

Ferrothorn's role is being the team leader, which sets up the spikes and paralyzes pokemon making mew able to outspeed them and have a better work as a special sweeper, leech seed allows ferrothorn to restore more hp each turn and is hepful against pokemon like heatran that dont recieve a lot of thamage from power whip, which is ferrothorn's best stab move and it can even OHKO ash.greninja. With evs oriented to a defensive role.

Tapu Fini @ Leftovers
Ability: Misty Surge
EVs: 248 HP / 200 Def / 60 Spe
Bold Nature
IVs: 0 Atk
- Scald
- Moonblast
- Taunt
- Nature's Madness
Tapu Fini's role is being phisically defensive, nature´s madness is used to reduce half of the opponent´s health, which is very useful against really bulky pokemon, scald and moonblast are Tapu fini's better STAB moves, specially scald is preety useful with physicall sweepers because of the burn chance. and taunt for annoyer pokemon, pokemon with defog, and pokemon like toxapex.

Garchomp @ Garchompite
Ability: Rough Skin
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Swords Dance
- Earthquake
- Iron Head
- Substitute
Garchomp's role is being a physical sweeper, swords dance is very useful to double its already really high attack, earthquake because its Garchomp's better STAB move, Iron head will be useful against fairy pokemon that can easily kill garchomp with their fairy attacks, and also for fairy ice pokemon like alolan ninetales, and substitute to avoid moves like toxic, will-o-wosp, or habilities like intimidate.

Heatran @ Leftovers
Ability: Flash Fire
EVs: 252 HP / 4 SpA / 252 SpD
Timid Nature
IVs: 0 Atk
- Lava Plume
- Toxic
- Protect
- Stealth Rock
Heatran's role is being a specially defensive pokemon, lava plume for STAB, toxic for bulky pokemon, protect to avoid moves like earthquake, and stealth rock because ferrothorn does not sets spikes and heatran stealth rock. Heatran can be changed when pokemon like garchomp can be atacked by super-effective moves and strongly resist them, like bug moves with mew, ice moves with garchomp, grass moves with tapu fini, or steel with Tapu Koko.

 

[LandoLando]

yo
The first thing I would maybe change is ferros choice of an attacking move. Gyro ball is usually a good move to have, but if you want to keep power whip, then at least remove the 0 speed ivs. If you're gonna have 0 speed ivs, you might as well have sassy nature and gyro ball.
Secondly, your team lacks hazard removal, which is greatly needed, as fini and tran can easily get chipped down by rocks or spikes. Tapu fini is a good defogger to have, and I recommend that you swap scald for it, as it is pretty useless other than possibly burning tapu bulu on the switch. scald will NOT help you against physical attackers as finis misty terrain prevents burns for 5 turns.
Thirdly, I like your idea with mega chomp, as you can encourage a swap and then sub on their swap to get a free sd, but iron head can be replaced with a better attack, even if it can hit fairies hard. You can still run it, but also consider something like stone edge, dragon claw, or maybe even fire fang.
Finally, you dont have to do this, but consider having earth power on heatran instead of protect, so you dont get hard walled and forced to swap by any opposing heatrans.
That's about it.

 

[Mew Primigenio]

Do you think I should change mew as special sweeper? Some people have recommended me to change it for another pokemon

 

[Robot7620]

Do you think I should change mew as special sweeper? Some people have recommended me to change it for another pokemon

Definitely, Mew is terrible at as a sweeper role.
First off, while it's a powerful nuke and summons Psychic Terrain, that in itself doesn't last long and the opposing team often carries at least one Tapu, and Lele shreds you.
Next, if you're gonna keep it, change that moveset. You get hard walled by Lele, and any other Tapu changes the terrain and can handle you relatively easily with the exception of Band Bulu that's within range after a boost.
But, I'd recommend Scarf lele or Specs Gren as a specials weeper; Mew generally runs a support role, able to provide massive utility with Rocks, Defogging, Status etc.

 

[DrPumpkinz]

Next, if you're gonna keep it, change that moveset. You get hard walled by Lele

Thanks to Lele setting up the terrain for you, +2 Genesis Supernova actually blows it back.
+2 252 SpA Mew Genesis Supernova vs. 0 HP / 4 SpD Tapu Lele in Psychic Terrain: 334-393 (118.8 - 139.8%) -- guaranteed OHKO

That said, swapping out Mew for Lele isn't the worst idea, but I wouldn't go with Scarf. I'd stick with setup + Z, as it synergizes well with Screens Koko.

Tapu Lele @ Fightinium Z
Ability: Psychic Surge
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Psychic / Psyshock
- Moonblast
- Focus Blast
- Calm Mind

 

[LandoLando]

Definitely, Mew is terrible at as a sweeper role.
First off, while it's a powerful nuke and summons Psychic Terrain, that in itself doesn't last long and the opposing team often carries at least one Tapu, and Lele shreds you.
Next, if you're gonna keep it, change that moveset. You get hard walled by Lele, and any other Tapu changes the terrain and can handle you relatively easily with the exception of Band Bulu that's within range after a boost.
But, I'd recommend Scarf lele or Specs Gren as a specials weeper; Mew generally runs a support role, able to provide massive utility with Rocks, Defogging, Status etc.

Mew may not be the most ideal sweeper there is, but he is far from terrible. I've managed to get so many sweeps and wins with Z-mewve (kill me) mew and he is no joke. Sure, ash gren and steela kind of wall him, but with them out of the question he can do what he wants. Set is below.

the gym lad

Mew @ Mewnium Z
Ability: Synchronize
EVs: 248 HP / 44 Def / 216 Spe
Timid Nature
IVs: 0 Atk
- Psychic
- Earth Power
- Nasty Plot
- Soft-Boiled