If you CAN manage to Crumple him with the Boombox effect also active on the first turn, yes, you can 1HKO him with Squirt Gun dealing a total damage potential of 380 (if he didn't die after only 300 damage).
But good luck Crumpling him in one sticker... my best guess is to use either Flashy POW Block or use a Leaf+Fishhook in battle to get a Megaflash Jump and use IT to Crumple him.
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