Fireyblaze000
PhoenixBlade983
BUG BUZZ
No that does not work. My Life orbed Modest Yanmega can't kill it in one hit.
According to Metalkid's damage calculator, 252 SAtk Modest LO Yanmega Bug Buzz always OHKOs 252HP/252SDef +SDef Nature Celebi under normal conditions. Maybe you used Air Slash instead, or Light Screen was up?

Possible problems with Crunch: Jolly SDChomp only has a small chance to OHKO after one SD.
On the other hand, 252 Atk Jolly DDTar with one DD (or 252 Atk Jolly CBTar) can always OHKO with Crunch. It may not be faster, though.