Nearly every trainer in the game has received significant changes — a total of 387 trainer encounters as well as raid ally changes (see Ally Raid Overhaul) and changes to partner teams during certain story events — bringing new Pokémon into their teams (in some cases, replacing them entirely), increasing their strength by increasing their team sizes (most of the time), and by providing increased IVs, EVs, new moves, and giving them better AI settings.
Additionally, around 25% of all trainer battles in the game are now doubles battles, including some Gym Leaders and other major fights at all stages of the game.
Note to players — Always carry two Pokémon with you.
Due to an issue in the base game, your game will crash if you are thrown into a Doubles battle with only a single Pokémon. See Crashing at the Start of Battles for more.
(Text has been modified at the beginning of the game to notify players of the above issue.)
As you progress through the game, all trainers will be given better moves (including TM and egg moves), higher stats (levels, IVs, and EVs), positive natures, held items, Terastallizing, etc., and better AI. Compass is meant to be progression-oriented, so early trainers will not be particularly strong, but the amount of pushback will steadily increase the further you go, until the later portions of the game that feature large teams with fairly-high “difficulty” values consistently.
New Pokémon added to trainer teams are not randomly chosen → Instead, they are manually determined based on trying to stay relatively close to the established theme of the trainer. This thematic choice is occasionally prioritized over optimized competitive teams, resulting in a few Major Trainers having little or even no difference in their Pokémon choices, though adjustments are universally made to IVs, EVs, etc.
All Trainers are broken up into two categories, “Minor” and “Major”, which is used to denote how strong the trainers are relative to each other.
Minor Trainers — those unrelated to any story that just hang around the world, or general grunts — make up the majority of all trainer fights in the game, and are the weakest trainers. Major Trainers include strong trainers (denoted by a black chatbox when you are close to them), Gym trainers and leaders, rival fights, and other story-related trainers.
Major Trainers in the same area are always going to be stronger than the Minor Trainers, with more Pokémon, higher levels, better movesets, increased stats, and access to other difficulty features earlier than Minor Trainers. Additionally, all Major Trainers have the capability to Terastallize their Pokémon and have the highest AI Settings enabled, allowing them to swap Pokémon if necessary and less randomly utilize their moves.
Major Trainers also reward the player with a significant amount of money.
Compass also increases the number of these “strong” trainers to more than double vanilla’s total.
Partner fights throughout the story are also changed to match the trainer’s other adjustments, whether that be level, team, stats, etc.
In the Post-Game Gym Circuit, all Gym Leaders will rematch you with level 83-85 aces (up from 66). They’ll be facing you with their toughest teams, and are amongst the most challenging fights in the game.
In the first Academy Ace tournament, each final Pokémon will be between levels 85 and 88 (up from 66 to 70). Similar to the Gym Leaders just prior, these fights are designed with strong teams in mind.
The second Academy Ace tournament, and each thereafter, as well as the Team Star rematches, are all set to level 100. They are also the highest general tier of difficulty, to serve as something to work toward while putting together your best teams. Many of their Pokémon have been changed, as well, while trying to stay close to the original theme of the trainer.
Nemona, Geeta, and the Professors are designed to be the toughest trainers in the entire game, but aren’t significantly increased relative to the overall strength of the post-game fights, largely because these other battles are nearly at the max values to begin with.
The repeatable Academy Ace tournament provides significantly increased money per victory, giving 32,000 Pokémonies each!