Team Fou-Lu vs Team Mewtwo (Fou-Lu, Kanon, Lyon, Thomas) vs (Mewtwo, Billy, Max, Black Wizard): Mewtwo drops Lyon in a doubled hit, Billy hastes him, Kanon and Thomas do something ineffectual (WA2 characters couldn't do anything good on their first turn right?), Fou-Lu does the MT HP ->1 thing. Next turn Mewtwo's 3x average speed. He buffs himself once then starts murdering everyone on the other team on doubleturns and tripleturns while Billy fully heals him. Fou-Lu gets off an MT attack which kills everyone but Mewtwo, who barely feels it and tears Fou-Lu apart. Alternatively Fou could try dispel, but that's just giving Billy a chance to heal himself, which dooms him just as well.
Go broken XG haste, not even Fou-Lu is cut out to deal with that.
Heavy/Godlike:
Ryu2, Millenia, Jecht, Miguel, Kanon, Billy
Jecht: 3-1. Petrify or delay poundings for all those PCs, but he can't outslug Miguel with his seriously inferior base damage and lack of elemental stuff.
Miguel: 3-1. Outslugs Jecht and Millenia, takes a hit from Ryu and 2HKOs, but he probably can't set up an OHKO vs. Billy who has elemental shielding nonsense to prevent an all-white field, so Billy hastes and grinds him out slowly.
Millenia: 2-2. Kills PCs (who aren't fast enough to shut her down), dies to bosses.
Ryu2: 1-3. Ryu doesn't OHKO either boss (Jecht has an HP buffer to save him even if you see the ITD overkill as good enough otherwise), and Millenia gets her SBE shenanigans going, but he swats billy like a gnat.
Billy: 1-3, this attrition shit only works on Miguel.
Middle/Heavy:
S5 Lyon, Elly, Mirage, Cloud, FE8 Lyon, Max
Lyon: 5-0. Outspeeds and 2HKOs everyone but Mirage who is faster but fails to 2HKO, and Lyon has status resistors to handle Elly.
Cloud: 3-2. Blocks sleep, so that takes care of Elly. Lyon and Max both get screwed by a limit because they don't chip. When cloud takes Lyon's counter, that immediately gives him a limit and thus a full ATB bar, so the order there is cloud swing, lyon counter, cloud swing (double), cloud limit, GG. He also gets a limit vs. Mirage but I don't think it's good enough without the status or a speed advantage.
Lyon: 2-3. Max and Other Lyon have the damage to one-round him with that initial double, while Cloud doesn't need it. Elly and Mirage get screwed.
Max: 2-3. Carves up Mirage and Lyon, everyone else has some sort of trickery to deal with him (well Lyon just explodes him.)
Elly: 2-3. Max and Mirage have no defense vs. sleep, everyone else does.
Mirage: 1-4. Messes up Cloud with her statusblockers and superior speed, dies to everyone else (they 2HKO her and aren't 2HKOed back)
Light/Middle:
Mara/Maya, Vincent Valentine, Opera, Noah, Thomas, Black Wizard
Meh.