252+ SpA Choice Specs Tera Fighting Hoopa-Unbound Focus Blast vs. 252 HP / 252+ SpD Blissey on a critical hit: 690-812 (96.6 - 113.7%) -- 81.3% chance to OHKO
most pedantic calc ever, but i think it actually helps your point, because chi yu was able to do this without a super effective move...