How high can one Pokemon boost its stats in one turn with no assistance?

Question

I'm making a team with costar flamigo, and I want it to have a partner that can boost its own stats really high in one turn so flamigo can copy it later.
I'm looking for a combo of moves, abilities, items, etc that can boost stats as much as possible in one turn. Thanks in advance!

Comments

i came up with medicham with the item roto boost, ability pure power, and acupressure but this is not a complete answer.

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This question if for Gen 9 so there are no Rotom Powers.

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I don't think it's possible to switch out Tatsugiri when commander is active.

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@sumwun You can switch a new Pokémon in for Tatsugiri if it faints, which is very hard to do, but not impossible. Wolfe Glick pioneered a somewhat gimmicky team based around this; Tatsu + Explosion Mon turn 1, use Endure + Explosion to drop down to 1 HP, then Tatsu gets poisoned by its Toxic Orb at the end of the turn. Switch in Dozo, then the poison kills Tatsu at the end of T2 and you’re free to switch in Flamigo.

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I think it's either just No Retreat Falinks, the Commander Toxic Orb Dondogiri tech, Belly Drum, or getting lucky with Ancient Power or Ominous Wind.

Answer 1

No assistance
Belly Drum: +6
Geomancy and power herb: +6
Fillet Away: +6
No Retreat: +5
Clangorous Soul: +5
Shell Smash: +4 (+6 if you ignore the drops or have a white herb)
Simple and any +2 move: +4
Scale Shot: 0 (+5 if you ignore the drops)

Requires some assistance
Simple beam and one of the +6 setups from above: +12
Rattled, weakness policy, and beat up: +10
Water compaction, weakness policy, and water shuriken: +10
Commander: +10
Weak armor, weakness policy, and super effective move that hits 5 times: +9 (+14 if you ignore drops)
Stamina, weakness policy, and super effective move that hits 5 times: +9
Steam engine, weakness policy, and water shuriken: +9
Anger point, weakness policy, and a guaranteed critical hit move: +8
Justified and beat up: +6 (no Pokemon with justified is weak to dark)
Weakness Policy: +4
Decorate: +4
Memento and contrary: +4

I think these are all the ways to get more than +3 boosts in one turn. Please comment if I missed any
source

Comments

Thank you!!!  my team is working very well with white herb shell smash :)

Answer 2

In a double battle I use Meowscarada’s Flower Trick on my Krookodile with the ability Anger Point. Because it is hit with a Critical Hit its attack stat gets maxed. Next turn you can swap Meowscarada for your Costar Flamingo.