Hyper Beam, if you don't count its brief reign of terror in gen 1. Its derivatives as well by extension.
Luster Purge / Mist Ball. They were obviously inteded for bulky Lati@s to cripple their checks, but with such a low chance of stat drops they're just useless.
Charge Beam. 10% chance to miss, 30% chance to not boost SpA, only 10 base power more than Power-Up Punch.