Moves
Blast Burn is Mega Charizard Y's most powerful move, as well as one of the most powerful moves in the metagame, able to neutralize almost any Pokemon it can hit super effectively, such as Magearna, Mega Metagross, Aegislash, and Celesteela, as well as frailer Pokemon that resist Fire-type damage, such as Naganadel. Beware of its recharge after usage, Blast Burn's biggest downside. Solar Beam is Mega Charizard Y's best coverage option, allowing it to hit several Water-type Pokemon, such as Guardian of Alola Tapu Fini, Calm Mind Mega Slowbro, and Mega Swampert. Flame Charge is a utility option that gives Mega Charizard Y a way to beat the common sleep inducer Jumpluff, alongside giving an extra bit of chip damage against faster threats such as Greninja, Mega Gardevoir, Substitute Mega Metagross, and Naganadel. Air Slash is Mega Charizard Y's secondary STAB option, used primarily to get a Pokemon in range of Blast Burn or break a Substitute from an opposing Pokemon that resists Solar Beam, such as Mega Venusaur and specially offensive Mega Altaria. It also has a noticeable 30% chance to make an opposing Pokemon flinch, which can be useful as a last-ditch effort against Pokemon such as Mega Aggron, Magnezone, specially defensive Tapu Lele, and Kommo-o. However, this is by no means a reliable strategy and should only be used if there is no other option in order to win. Will-O-Wisp can also be used to cut the Attack of bulky Mega Gyarados, removing its immediate offensive presence, alongside beating certain Sturdy Pokemon like non-Rockium Z or Choice Band Avalugg and FEAR Aron. You can also choose to run Hidden Power Electric, which, along with Solar Beam, always 2HKOes offensive Mega Gyarados and forces a mind game with bulky Mega Gyarados; this only has use against Mega Gyarados, however. Substitute can be used to lure in Head Smash Donphan and Aggron, two Sturdy users that can OHKO Mega Charizard Y if they can land their attack, OHKOing with Blast Burn after recoil damage. Rock Tomb can be run in order to beat opposing non-Rock Tomb Mega Charizard Y.
Set Details
116 HP and 8 Special Defense EVs allow Mega Charizard Y to tank attacks like Choice Specs Hydro Cannon from Greninja, Choice Specs Draco Meteor from Naganadel, as well as take a burned Avalugg's Stone Edge. Mega Charizard Y also runs 216 Speed EVs with a Timid nature in order to outspeed base 95 Speed Pokemon such as Tapu Lele as well as slower Pokemon such as non-Choice Scarf Landorus-T, non-Choice Scarf Z Porygon-Z, and Vivillon. The rest goes into Special Attack, in order to improve Mega Charizard Y's matchups against bulkier Pokemon such as Mega Sableye and Mega Slowbro.
If you're running Will-O-Wisp, Mega Charizard Y can potentially run a bulky offense spread of 124 HP / 68 Def / 108 SpA / 208 Spe and a Modest nature in order to outspeed and beat every variant of Mega Gyarados, not just bulky Mega Gyarados. If Hidden Power Electric is being used, 8 HP / 148 Def / 144 SpA / 208 Spe and a Modest nature can be run, which simply outspeeds Mega Gyarados and tanks any of its attacks boosted by a Dragon Dance. Mega Charizard Y can also run 208 HP / 116 SpD / 184 Spe and a Timid nature in order to survive a Modest Hyper Beam from Choice Scarf Porygon-Z, allowing it to beat all sets, as well as outspeeding non-Choice Scarf Landorus-T.
Usage Tips
Blast Burn does nominally more damage than its coverage options against Pokemon that it hits neutrally with Blast Burn, such as Krookodile. However, if the coverage moves can still knock the Pokemon out, they should be used, in order to avoid missing your move and losing the game. Choice Specs Greninja can try to change its type with Protean to avoid fatal damage from Solar Beam, and thus using Flame Charge turn one, followed up by either Solar Beam or Blast Burn, will allow Mega Charizard Y to react to every play an opposing Greninja can make and avoid any mind games. For specially offensive Mega Altaria, spam Air Slash. Air Slash's absurd 30% flinch chance, combined with Mega Charizard Y's excellent Special Attack, and Mega Charizard Y's resistance to Mega Altaria's Fairy-type will ensure that Mega Charizard Y will waste the recovery option and get them into range of Blast Burn through flinches. If you are running the anti-Mega Gyarados Will-O-Wisp spread, use Will-O-Wisp turn one, followed by a Solar Beam turn two, and Blast Burn turn three in order to have the best chances to beat bulky Mega Gyarados. If you're running Hidden Power Electric, be aware that Hidden Power Electric into a Solar Beam against a bulky Mega Gyarados can sometimes fail to KO, if they Mega Evolve turn one. Therefore, predicting if they will choose to Mega Evolve or stay in base form can aid you, although the odds of winning against bulky Mega Gyarados if you predict incorrectly turn one is still very much in your favor.
Team Options
Mega Charizard Y is naturally weak to several Rock-, Electric-, and Dragon-type Pokemon, such as Mega Tyranitar, Magnezone, and Zygarde, alongside Mega Gyarados; this makes it fit extraordinarily well with a standard Fire / Water / Grass core, which can fill in its deficits using Pokemon such as Tapu Fini, Mega Gyarados, Mega Venusaur, and Jumpluff. In return, these Pokemon appreciate Mega Charizard Y's positive matchup against all other Grass-type Pokemon as well as common Steel-type Pokemon such as Magearna and Genesect. Mega Charizard Y also works well with Ground- and Dragon-type Pokemon that can beat back the aforementioned Rock- and Electric-type Pokemon, as well as opposing Fire-type Pokemon like Heatran, Victini, and Incineroar. Pokemon such as Zygarde, bulky Donphan, Kommo-o, and Dragonite can beat all of these threats. In return, Mega Charizard Y threatens Ice-type Pokemon or Pokemon wielding Ice-type moves, such as Greninja, Genesect, Kyurem, Avalugg, and Alolan Ninetales, and bulky Water-types like Tapu Fini and Mega Blastoise. Mega Charizard Y also has issues against specially defensive stall Pokemon, such as Amnesia Mega Slowbro, Stored Power Necrozma, Porygon2, and Chansey. Because of this, stallbreakers such as Taunt + Crunch Mega Gyarados, Mega Heracross, and Vivillon all make excellent partners to Mega Charizard Y, which can, in return, beat threatening Pokemon to them such as Mega Metagross and Mega Gardevoir.