Comprehensive list of all the pokemon on Smogon that cannot be 2hkoed by CB Rampardos (with headsmash, outrage, eq, zen headbutt):
Groudon (Support) Outrage 36.38 - 42.82% Head Smash 33.66 - 39.85%
Hippowdon (Physical Wall) Outrage 39.28 - 46.42% Head Smash 36.66 - 43.33%
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