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

Ho-Oh:
Teach EQ/Psychic over Recover/Sunny Day
Icefall Cave Rocket: Swift x3 (Golbat 100% with 180+ Atk (19+/0+/0+))
Teach Shock Wave over Swift
Five Island Rocket Grunt: SW, Psychic/FB
Warehouse Grunt: EQ x2 (100% with 184+ Atk (26+/0+/0+)
Admin 1: EQ, FB/Psychic, Psychic (Vileplume Psychic 100% with 167+ Sp. Atk (x/12+/0+))
Admin 2: Psychic (100% with 148+ (9+/0+/0+)), Psychic (100% with 147+ (8+/0+/0+)), EQ
Gideon: Swift/Psychic, EQ x4 (faster than Electrode with 4+/0+/0+)
PC Heal + deposit mons
Lorelei: EQ + X-Attack + EQ Dewgong, SW Cloyster, FB Piloswine, EQ Jynx, EQ x2 Lapras (FB does around the same, can fill in if one is better than other)

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