Like I said this set can make Mew counter Volcarona:
Mew @ Tanga Berry
Ability: Synchronize
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Calm Mind
- Psyshock
- Power Gem
- Fire Blast
Or this Physical variant:
Mew @ Tanga Berry
Ability: Synchronize
EVs: / 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Dragon Dance
- Psychic Fangs
- Stone Edge
- Flare Blitz
However on Offensive Quiver Dance sets they have a speed tie. If Mew can win the speed tie before Volcarona sets up Quiver Dance, Mew can probably OHKO it in return. Dragon Dance will allow Mew outspeed Volcarona.
252 SpA Volcarona Bug Buzz vs. 4 HP / 0 SpD Tanga Berry Mew: 153-180 (44.7 - 52.6%) -- 21.9% chance to 2HKO
252 SpA Volcarona Bug Buzz vs. +1 4 HP / 0 SpD Tanga Berry Mew: 102-120 (29.8 - 35%) -- 14.1% chance to 3HKO
252 Atk Mew Stone Edge vs. 0 HP / 4 Def Volcarona: 516-608 (165.9 - 195.4%) -- guaranteed OHKO
252 SpA Mew Power Gem vs. 0 HP / 0 SpD Volcarona: 280-332 (90 - 106.7%) -- 43.8% chance to OHKO
+1 252 SpA Mew Power Gem vs. 0 HP / 0 SpD Volcarona: 420-496 (135 - 159.4%) -- guaranteed OHKO
This is the Bulky Quiver Dance calcs:
16 SpA Volcarona Bug Buzz vs. 4 HP / 0 SpD Tanga Berry Mew: 127-151 (37.1 - 44.1%) -- guaranteed 3HKO
+1 16 SpA Volcarona Bug Buzz vs. 4 HP / 0 SpD Tanga Berry Mew: 190-225 (55.5 - 65.7%) -- guaranteed 2HKO
252 Atk Mew Stone Edge vs. 248 HP / 156 Def Volcarona: 420-496 (112.6 - 132.9%) -- guaranteed OHKO
252 SpA Mew Power Gem vs. 248 HP / 0 SpD Volcarona: 280-332 (75 - 89%) -- guaranteed 2HKO
+1 252 SpA Mew Power Gem vs. 248 HP / 0 SpD Volcarona: 420-496 (112.6 - 132.9%) -- guaranteed OHKO
Mew @ Tanga Berry
Ability: Synchronize
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Calm Mind
- Psyshock
- Power Gem
- Fire Blast
Or this Physical variant:
Mew @ Tanga Berry
Ability: Synchronize
EVs: / 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Dragon Dance
- Psychic Fangs
- Stone Edge
- Flare Blitz
However on Offensive Quiver Dance sets they have a speed tie. If Mew can win the speed tie before Volcarona sets up Quiver Dance, Mew can probably OHKO it in return. Dragon Dance will allow Mew outspeed Volcarona.
252 SpA Volcarona Bug Buzz vs. 4 HP / 0 SpD Tanga Berry Mew: 153-180 (44.7 - 52.6%) -- 21.9% chance to 2HKO
252 SpA Volcarona Bug Buzz vs. +1 4 HP / 0 SpD Tanga Berry Mew: 102-120 (29.8 - 35%) -- 14.1% chance to 3HKO
252 Atk Mew Stone Edge vs. 0 HP / 4 Def Volcarona: 516-608 (165.9 - 195.4%) -- guaranteed OHKO
252 SpA Mew Power Gem vs. 0 HP / 0 SpD Volcarona: 280-332 (90 - 106.7%) -- 43.8% chance to OHKO
+1 252 SpA Mew Power Gem vs. 0 HP / 0 SpD Volcarona: 420-496 (135 - 159.4%) -- guaranteed OHKO
This is the Bulky Quiver Dance calcs:
16 SpA Volcarona Bug Buzz vs. 4 HP / 0 SpD Tanga Berry Mew: 127-151 (37.1 - 44.1%) -- guaranteed 3HKO
+1 16 SpA Volcarona Bug Buzz vs. 4 HP / 0 SpD Tanga Berry Mew: 190-225 (55.5 - 65.7%) -- guaranteed 2HKO
252 Atk Mew Stone Edge vs. 248 HP / 156 Def Volcarona: 420-496 (112.6 - 132.9%) -- guaranteed OHKO
252 SpA Mew Power Gem vs. 248 HP / 0 SpD Volcarona: 280-332 (75 - 89%) -- guaranteed 2HKO
+1 252 SpA Mew Power Gem vs. 248 HP / 0 SpD Volcarona: 420-496 (112.6 - 132.9%) -- guaranteed OHKO