Mega Costume required P1 counter 3 times, star punch for 3 (1/5 chance he doesn't uppercut and you miss), then counter 3 more times for a KD. P2 counter once, then star punch and GMP to KD. P3 counter the rush
This LOOKS slower than the current record, but that's because that one has ghost glitch (patched) and is still up for some reason.