Mega Manectric as a check.
Manectric @ Manectite
Ability: Lightningrod
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
- Thunderbolt
- Volt Switch
- Hidden Power Ice
- Overheat / Flamethrower
Manectric is one of the best checks to Magnezone, being able to resist its STAB combination, while also acting as a great switchin pre-mega, as it forces Magnezone to think before going for Volt Switch to try and get momentum off of it. Specs Thunderbolt is a 2HKO on Manectric, and so is Flash Cannon after Rocks, but Manectric can force it out by threatening it with Fire coverage like Overheat which OHKO's and Flamethrower which kills with prior damage:
252 SpA Mega Manectric Overheat vs. 76 HP / 0 SpD Magnezone: 318-376 (106 - 125.3%) -- guaranteed OHKO
252 SpA Mega Manectric Flamethrower vs. 76 HP / 0 SpD Magnezone: 222-262 (74 - 87.3%) -- guaranteed 2HKO
252+ SpA Choice Specs Magnezone Thunderbolt vs. 0 HP / 0 SpD Mega Manectric: 145-171 (51.6 - 60.8%) -- guaranteed 2HKO
252+ SpA Choice Specs Magnezone Flash Cannon vs. 0 HP / 0 SpD Mega Manectric: 129-153 (45.9 - 54.4%) -- guaranteed 2HKO after Stealth Rock