All the OHKO moves - Fissure / Guiollotine / Sheer Cold / Horn Drill. The question here is if No Guard boosts the OHKO moves to 100% (no miss) or would they remain the same accuracy at 30%?
Yes, OHKO moves used by Pokemon with No Guard will always hit. To be specific, this works by skipping the accuracy check altogether, not by increasing accuracy to 100%.
...any effects that cause a move to completely ignore the accuracy check (such as the Ability No Guard, or X Accuracy in Generation II or earlier) will allow OHKO moves to always hit.
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There are no Pokemon that with No Guard that can (legally) learn OHKO moves.
Yes it does, but since no Pokemon with No Guard learns any of the OHKO you mentioned, it can only be tested by hacking or Showdown. Also, OHKO moves are banned by Smogon and cannot be used in STABmons.
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