Sae
In the midst of Orre
You're not thinking in terms of the entire team though. MegaY literally defines Fire Monotypes. By itself from full health, it can threaten almost every single Water type with Solar Beams and it won't usually die from one hit from water mons thanks to Sun being out. The only water types that can counter, being able to to take a hit on the switch and beat it one v one, are normally Tentacruel and Sap Sipper Azu since everything else gets 2HKO'd at best or just outright OHKO'd. Also, setting up Sun for Fire teams allow it the rest of team to function: V-Create/Blue Flare spam from Victini, Flare Blitz from Entei or Darmanitan, etc. Also it allows other mons like Specially Defensive Heatran to take on things like Latios without worrying about Surf as much allowing Heatran to give residual damage via status and lava plumes to Latios or setup SR. Also Keldeo is a check to MegaY, not an outright counter.I disagree and think mega zard Y should be A Rank for fire teams.
This version of charizard will be forced out by the likes of keldeo, latios, and thundrus-I which are all on everyteam's watch list, therefore most prepared team will have something for it. Worse for charizard, if they use something lando-t a volturn or terrakion, for this job... then you put your already overworked defensive pokemon at risk, especially if an expected stone edge or volt turn turns into a stealth rock or substitute. Enhancing its own and your team's ability to hammer walls is difficult to capitalize on when their first response to a KO threatens to force you to chose between the core of your offense or defense.
- 252 SpA Choice Specs Keldeo Hydro Pump vs. 0 HP / 0 SpD Mega Charizard Y in Sun: 236-278 (79.4 - 93.6%) -- guaranteed 2HKO
- 252 SpA Mega Charizard Y Solar Beam vs. 0 HP / 4 SpD Keldeo: 330-390 (102.1 - 120.7%) -- guaranteed OHKO
Yeah in a 1v1 situation first turn, Keldeo can't even OHKO with specs meaning that Keldeo is forced out first turn. Debatable point since Keldeo will just switch into Tentacruel or Sap Sipper Azumarill, but if the water team doesn't carry that, something's going to die. Maybe the Keldeo will stay in and sacrifice itself so MegaY is forced out next turn and thus can't setup sun, or maybe Keldeo misses the hydro and you lose your check. Yeah Mega Y can carry a Fire team in a Water v Fire matchup. Also against Politoed which does rain, technically the mega comes after so you get a free Drought against Politoed the turn you mega.
So basically MegaY gives Fire the ability to play against it's most common weakness. Also most things still don't appreciate taking a Sun boosted Fire Blast, and in cases of rock types like Terrakion, a smart player could just predict Solar Beam.
In cases like VoltTurn offense, most common users are: bug teams, flying teams, electric teams. Maybe Volt Switch will cause a slight loss in momentum from Electric, but between Heatran and Rotom-H it should be manageable. In cases of bug teams, lol what's to fear. In cases of Flying teams, most people on Fire teams use their own pivot Scarfs against them like Rotom-H or Victini (which can run Glaciate js).
So yes MegaY can be beaten by these things, but a well prepared fire team has ways around them, and a good player will bait out certain threats. This doesn't mean that it's plagued to the point that it's A rank. No, MegaY is definitely S-rank. Is there anything else you want me to bring up? I can reply to any other arguments you or anyone else may say, but I'm pretty sure majority of Fire users would vehemently defend Mega Y's spot as S rank so I'm not alone.