(Both, 1) No initial megas from either side. This should be fun.
(R, 1) Scald into a Water Absorber.
(L, 1) Flame Charge Volcanion is a niche pick already, but it uses it on Omastar, a 4x resist.
(L, 2) Volc reveals Focus Blast, which smacks everything for neutral damage...except when it doesn't.
(L, 3) Brick Break. If this is supposed to be a Blob lure, it gets Superpower. And why not use this instead of risking Focus Blast? Like, period?
(R, 3) Standard, physical Mega Ampharos. And Thunder Punch when it gets Wild Charge.
(R, 5) At least it has Iron Tail to kill Fairies.
(L, 5) Healing Wish Mega Latias, used on the first turn. Even if that Ampharos had Outrage, Lati can probably take it, assuming it didn't Draco the poor bastard. Anyway, HW into...
(L, 6) Mega Latios, which does Draco.
(L, 7) Yeah, how much do you think a -2 resisted Ice Beam is going to do?
(R, 7) Burn fishing, are we?
(L, 8) Draco crit. Always rewarded for bad play.
(R, 9) Blizzard Miltank. Which misses. Granted, 40 SpA against 120 SpD isn't going to end well even with type advantage. (24% when it does hit on the next turn.)
(L, 10) Volcanion, which 4x-resists Blizzard and has not one but two Fighting moves, is just sitting on the bench while Latios cripples itself.
(L, 11) Latios reveals HP Fighting. It does even less.
(Both, 12) Double miss.
(L, 13) Now we switch. Into a...
(R, 13)...Rollout. Whitney would not be proud. Also, horrible luck there.
(R, 16) Crit on the fourth turn, 61%, which puts Giratina pretty low.
(L, 16) Twister. I have lost all ability to even.
(L, 18) Mega Mewtwo Y with Poison Jab. Just why.
(Both, 19-21) Mewtwo gets 1v1'd by a Fearow (thanks to a Sitrus).
(L, 22-25) Life Orb Mew with Psyshock/Dazzling Gleam. Finally! Something approaching normal!
(R, 23) Stop Substituting, Pidgeot. It doesn't work.
(R, 25-32) Screens/Toxic/Protect Meganium. Another set I actually recognize.
(L, 29) Sure, now you Ice Beam. And, because bad play is always rewarded, it scores a freeze.
(L, 31) Dragon Claw, Mew? Really?
(L, 33) Physical Mega Pidgeot. Sigh.
(Both, 33) It ultimately ends when Mew survives a Return only to Life Orb itself out. It misses out on the Self-KO Clause trigger by 2%.