u/Enough-Caregiver-704

I've been trying to do the Robin achievement, but I just can't get it. I have KOed a level 9 CPU with the rapid jap in a 2-player battle within 3 minutes, spirits off, and without handicaps, but it just won't give me the achievement. Is there something I'm doing wrong? Sorry for not posting a video, Reddit won't let me for some reason.