Against Mewtwo (NOT considering Cerulean Cave encounters, but Mewtwo comp on original hardware):
Ho-Oh: +3s
Lugia: +23s
Deoxys: -48s

Ho-Oh:
Teach EQ/AA/SW over Recover/Sunny Day/Swift
Icefall Cave Rocket: AA x3
Five Island Rocket Grunt: AA, FB
Warehouse Grunt: EQ x2 (100% with 184+ Atk (26+/0+/0+)
Admin 1: EQ, FB, Psychic, EQ
Admin 2: FB x2, EQ
Gideon: EQ x5 (faster than Electrode with 4+/0+/0+)
PC Heal + deposit mons
Lorelei: X-Attack, AA x2, SW/FB, FB, EQ x2 / EQ + FB, AA
	(FB does around the same to Lapras, can fill in if one is better than other) 
	(faster than Jynx with 138+ Speed (29+/7+/0+))
Bruno: FB, X-Attack, AA x3, FB (Machamp 100% with 31/1+/0+)
Agatha: X-Special x2, X-Speed, X-Acc, FB all but Crobat (SW)
	Can skip X-Speed with 165+ Speed (x/x/20+)
Lance: X-Special x4, X-Speed, SW, SW x2, SW x2, SW, SW x2
	Can finish setup on Dragonite if too many DDs
	faster than Aerodactyl at +1 with 127+ Speed (6+/0+/0+)
Champ: X-Defense, X-Attack x5-6, X-Speed, AA, X-Speed, AA, EQ x3, AA
	faster than Heracross with 137+ Speed (17+/0+/0+)
	+4 AA Gyara a decent range


Lugia:
Teach EQ/Psychic/Waterfall over Recover/Swift/Rain Dance
Icefall Cave Rocket: Waterfall x3 (Psychic with -Sp.Atk)
Five Island Rocket Grunt: WF, Psychic
Warehouse Grunt: X-Attack, EQ x2
Admin 1: Psychic (100% with 138+ (x/10+/0+), Psychic x2
Admin 2: Psychic x2, EQ
Gideon: WF, Psychic (Electrode), WF (Magnemite), HP/EQ (Magneton), Psychic (Porygon)
Lorelei: X-Special + Psychic + X-Special + Psychic, Psychic (Cloyster), WF (Piloswine), EQ x2 Jynx, Psychic x2 Lapras
Bruno: (Guard Spec?) + X-Special x2 + WF Steelixs, Psychic Hitmons + Machamp
PP Item
Agatha: (X-Speed with 162-(23-/x/x) Speed) + X-Special + Psychic Gengar, Crobat, WF + Psychic Misdreavus, Psychic Arbok + Gengar
Lance: X-Special x5, Psychic x5 (can WF Aero to give you an extra PP for Dragonite range) (Dragonite 2 100% 147+ (x/12+/0+))
	Can also kill Gyara at +4 (very good range) and setup the 5th on Dnite 1 if it has setup a lot
	Slower than Aero, does ~1/3
Heal, PP Item
Champ: (Guard Spec?), (X-Speed if 165- Speed (21-x/x/), X-Special x3, Psychic, WF x2, HP, Psychic x2, HP, Psychic 
	Skip the 3rd X-Special if upper end Sp. Atk