Are you sure? I swear I used a gameshark to give my machamp fissure for the laughs once and missed as much as normal.
I suppose it's possible that I did this with Butterfree's Compound Eyes though.
I forgot about the case that Panthera described where the OHKO attack fails against higher level Pokemon. However, I interpret that as being part of immunity because the attack will never work No Guard or not as opposed to the attack missing. If you were to use Lock On then an OHKO attack, it would still fail.
Still miss against a higher leveled opponent though IIRC. And they have a weird interaction with stuff like Protect (where apparently the formula is (100 - X)% with X being the usual accuracy of the attack, which means lower accuracy attacks are more likely to work). Given the ludicrously literal and absurd approach to No Guard that's being used here, Machamp's low speed means Bullet Punch is the best bet, and that's going to have 0 accuracy due to how weird No Guard is when put against shield like tactics. Also, fighting types are weak to psychic attacks. This means their brain is a weakness. That means a bullet to the brain should win, which Ocelot can deliver. This is significantly less implausible than "No Guard warps reality so attacks hit from fifty million miles away", so it's pretty safe to go with.
That quirk was actually fixed as of Platinum and is actually a negative for Machamp. If the shield is capable of blocking Machamp's attacks, the attack will be blocked. The Fortune deflector shield would be able to deflect Bullet Punch.
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SuperNiceDog was not so nice to my bracket.
Congrats to SuperNiceDog for winning the Rivalry Rumble Guru Contest!