Ability₁₅₅-No Guard (ft. Guaranteed OHKO)

💥In Battle💥
All moves used by or against a Pokémon with this Ability cannot miss (and are 100%).
⚠️It also allows Pokémon to be hit during the semi-invulnerable turn of Fly, Bounce, Dive, Dig, Shadow Force, Sky Drop, and Phantom Force.
⚠️It does not bypass type immunities.

⚠️A Tatsugiri hidden inside a Dondozo's mouth via the Commander Ability is immune to the effects of No Guard.

⚠️In Diamond and Pearl, a Pokémon with No Guard can successfully hit a Pokémon that has used Protect or Detect, but only if it uses a move with less than 100% accuracy. The lower the initial accuracy of the move, the higher its chance of breaking through Protect or Detect. Thus, when used against Protect or Detect, moves that never miss (such as Swift and Aerial Ace) will always be blocked.
⚠️One-hit knockout moves are exempted from this behavior and will be protected against. This battle mechanic was a bug, and was fixed in Platinum so that most moves are blocked by Protect and Detect.
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🛤️Outside Of Battle🛤️
Outside of battle, if a Pokémon with No Guard is in the first place in the party (even if fainted), the wild Pokémon encounter rate increases by 100%.
(It shares this property with Arena Trap and Illuminate.)

🔴Gen⁸
In Pokémon Sword and Shield, this Ability only affects the rate at which random encounters happen.

🟡Gen⁹
In Pokémon Scarlet and Violet, this Ability has no effect outside of battle.
~Bulbapedia