All information courtesy of Mnchngrngs

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TRAINER IVs
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GYM LEADERS
Roxanne: 12 IV (ace 24 IV)
Brawly: 12 IV (ace 24 IV)
Wattson: 20 IV (L22s are 26/27 IV, ace is 30 IV)
Flannery: 30 IV (L24s are 24 IV)
Norman: 24 IV (ace 30 IV)
Winona: 25/26 IV (L30/31s are 26/27 IV, ace is 31 IV)
Tate & Liza: 30 IV
Juan: 24 IV (ace 30 IV)
 
ELITE FOUR
Sidney: 30 IV (ace 31 IV)
Phoebe: 30 IV (ace 31 IV)
Glacia: 30 IV (ace 31 IV)
Drake: 30 IV (ace 31 IV)
Wallace: 31 IV

BOSS TRAINERS
Rival 1: 0 IV
Rival 1.5 (Rustboro): 3 IV (ace 6 IV)
Rival 2: 6 IV (ace 12 IV)
Rival 3: 12 IV (ace 18 IV)
Rival 4 (Lilycove): 18 IV (ace 24 IV)

Magma Admin Tabitha: 9 IV
Maxie 1: 18 IV
Maxie 2: 18 IV
Aqua Admin Shelly 1: 6 IV
Aqua Admin Matt: 6 IV
Aqua Admin Shelly 2: 12 IV
Archie: 18 IV

Mauville Wally: 3 IV
Victory Road Wally: 18 IV (ace 30 IV)

Steven: 31 IV

OTHER TRAINERS
Gabby&Ty 1: 6 IV
Gabby&Ty 2: 12 IV
Gabby&Ty 3: 18 IV
Gabby&Ty 4: 24 IV
Gabby&Ty 5: 30 IV
Gabby&Ty 6: 30 IV

Pokemon Breeders: 1 IV
Pokemon Rangers: 6 IV
Cooltrainers: 0 IV (double battlers), 12 IV (most) or 31 IV (Petalburg Gym)

Other trainers: Varies

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TRAINER HEALING ITEMS
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GYM LEADERS
Roxanne: 2 Potions
Brawly: 2 Super Potions
Wattson: 2 Super Potions
Flannery: 2 Hyper Potions
Norman: 2 Hyper Potions
Winona: 2 Hyper Potions
Tate & Liza: 4 Hyper Potions
Juan: 2 Hyper Potions
 
ELITE FOUR
Sidney: 2 Full Restores
Phoebe: 2 Full Restores
Glacia: 2 Full Restores
Drake: 2 Full Restores
Wallace: 4 Full Restores

BOSS TRAINERS
Maxie 1: 2 Super Potions
Maxie 2: 2 Super Potions
Aqua Admin Matt: 1 Super Potion
Archie: 2 Super Potions

Victory Road Wally: 2 Full Restores
 
Steven: 4 Full Restores

OTHER TRAINERS
All Pokemon Rangers: 1 Full Restore
 
Cooltrainer Wilton: 1 Super Potion
Cooltrainer Brooke: 1 Super Potion
Cooltrainer Johnathan: 1 Hyper Potion
Cooltrainer Marcel: 1 Hyper Potion
Cooltrainer Gerald: 1 Hyper Potion
Cooltrainer Ruben: 1 Hyper Potion
Cooltrainer Athena: 1 Hyper Potion
Cooltrainer Halle: 1 Full Restore
Cooltrainer Marley: 1 Hyper Potion
Cooltrainer Jazmyn: 1 Hyper Potion
Cooltrainer Diane: 1 Full Restore
Cooltrainer Katelyn: 1 Full Restore
Cooltrainer Quincy: 1 Full Restore
Cooltrainer Felix: 1 Full Restore
Cooltrainer Randall: 1 Hyper Potion
Cooltrainer Parker: 1 Hyper Potion
Cooltrainer George: 1 Hyper Potion
Cooltrainer Berke: 1 Hyper Potion
Cooltrainer Braxton: 1 Hyper Potion
Cooltrainer Vincent: 1 Full Restore
Cooltrainer Leroy: 1 Full Restore
Cooltrainer Edgar: 1 Full Restore
Cooltrainer Albert: 1 Full Restore
Cooltrainer Samuel: 1 Full Restore
Cooltrainer Vito: 1 Full Restore
Cooltrainer Owen: 1 Full Restore
Cooltrainer Warren: 1 Full Restore
Cooltrainer Mary: 1 Hyper Potion
Cooltrainer Alexia: 1 Hyper Potion
Cooltrainer Alexa: 1 Full Restore
Cooltrainer Jody: 1 Hyper Potion
Cooltrainer Keira: 1 Full Restore
Cooltrainer Carolina: 1 Hyper Potion
Cooltrainer Jennifer: 1 Full Restore
Cooltrainer Hope: 1 Full Restore
Cooltrainer Darcy: 1 Hyper Potion
Cooltrainer Cristin: 1 Hyper Potion
Cooltrainer Leonel: 1 Hyper Potion
Cooltrainer Shanon: 1 Full Restore
Cooltrainer Michelle: 1 Full Restore
Cooltrainer Caroline: 1 Full Restore
Cooltrainer Julie: 1 Full Restore
 
Lady Cindy: 1 Full Restore
Lady Daphnie: 1 Full Restore
Lady Brianna: 1 Full Restore
Lady Naomi: 1 Full Restore
Lady Sarah: 1 Full Restore
 
Expert Makayla: 1 Hyper Potion
 
Rich Boy Winston: 1 Full Restore
Rich Boy Garret: 1 Full Restore