Magnezone @ Leftovers
Ability: Sturdy
Level: 50
EVs: 252 HP / 252 SpD / 4 Spe
Calm Nature
IVs: 0 Atk
- Psych Up
- Shock Wave
- Flash Cannon
- Substitute
Magnezone is immune to Sheer Cold, resists Freeze Dry, sets up free Substitutes all over Glalie's face while copying Moody boosts with Psych Up.
Shock Wave never misses. Flash Cannon hits harder when Evasion is not a factor.
The EV spread gives you the highest possible Lefties number at level 50 and maximizes special bulk to tank Freeze-Dry better.
4 Speed EVs for the mirror match.
Nobody runs this much offensive investment on their Moody Glalie, so the calcs would be even better in practice.
+0 252 SpA Glalie Freeze-Dry vs. 252 HP / 252+ SpD Magnezone: 17-21 (9.6 - 11.8%) -- possibly the worst move ever
+2 252 SpA Glalie Freeze-Dry vs. 252 HP / 252+ SpD Magnezone: 33-40 (18.6 - 22.5%) -- possible 6HKO after Leftovers recovery
0 SpA Magnezone Shock Wave vs. 172 HP / 84 SpD Glalie: 46-55 (25.9 - 31%) -- guaranteed 4HKO
0 SpA Magnezone Flash Cannon vs. 172 HP / 84 SpD Glalie: 122-146 (68.9 - 82.4%) -- guaranteed 2HKO
You can consider Magnet Rise for the uncommon Earthquake Glalie, but that would come at the cost of valuable coverage or Substitute.
PS: All the entries with slashed move and/or item choices should be disqualified by default. Rule number one clearly states...