Aerodactyl-Mega @ Aerodactylite
Ability: Tough Claws
EVs: 252 HP / 80 Atk / 176 Def
Impish Nature
- Rock Slide
- Ice Fang
- Protect
- Rain Dance
- outspeeds Garchomp (and therefore Char Y) without needing speed investment
- 80 Atk OHKOs Garchomp with Ice Fang and easily OHKOs Char Y with Rock Slide
- Defensive investment survives a crit stone edge (because high crit chance) and you even survive Rough Skin damage on top of the crit stone edge (even though this chomp has blaze)
- Rain Dance because after I beat you 2v1, Im taking away your sun as well
Turn 1: Rock Slide and survive a Crit Stone Edge
80 Atk Mega Aerodactyl Rock Slide vs. 4 HP / 0 Def Mega Charizard Y: 408-484 (136.9 - 162.4%) -- guaranteed OHKO
252 Atk Garchomp Stone Edge vs. 252 HP / 176+ Def Mega Aerodactyl: 188-222 (51.6 - 60.9%) -- guaranteed 2HKO
Turn 2: Ice Fang Garchomp
80 Atk Tough Claws Mega Aerodactyl Ice Fang vs. 4 HP / 0 Def Garchomp: 360-424 (100.5 - 118.4%) -- guaranteed OHKO
maths: 60.9*1.5[crit]+(1/16*100)[rough skin]= 97.6
Note: If you want to say "well what if they protect" then you start putting predictions into the mix, and if the opponent can predict and use protect then so can I.