In addition to Sturdy's previous effect, Sturdy now works like a Focus Sash, causing the Pokémon to have 1 HP remaining if an attack's hit would have brought it from full health to 0 HP. Sturdy will activate as long as a Pokémon has full HP, and can therefore be used multiple times if brought back to full health. If a Pokémon with Sturdy is holding a Focus Sash, Sturdy will activate first. Final Gambit will KO a Pokémon with Sturdy even if its HP is full. -Bulbepedia
Sturdy will activate, as long as the Pokemon has full HP.
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