Mega Gardevoir VGC 2015 set calculations.

Gardevoir @ Gardevoirite
Ability: Trace
Level: 50
EVs: 68 HP / 84 Def / 60 SpA / 180 SpD / 116 Spe
Bold Nature
IVs: 0 Atk
- Protect
- Energy Ball
- Psyshock
- Hyper Voice

Defensively:

252+ SpA Aegislash-Blade Flash Cannon vs. 68 HP / 180 SpD Mega Gardevoir: 114-134 (75 - 88.1%) -- guaranteed 2HKO
252+ SpA Heatran Flash Cannon vs. 68 HP / 180 SpD Mega Gardevoir: 102-122 (67.1 - 80.2%) -- guaranteed 2HKO
252+ SpA Chandelure Shadow Ball vs. 68 HP / 180 SpD Mega Gardevoir: 110-132 (72.3 - 86.8%) -- guaranteed 2HKO
252 SpA Gengar Sludge Wave vs. 68 HP / 180 SpD Mega Gardevoir: 110-132 (72.3 - 86.8%) -- guaranteed 2HKO
252 SpA Life Orb Hydreigon Dark Pulse vs. 68 HP / 180 SpD Mega Gardevoir: 60-71 (39.4 - 46.7%) -- guaranteed 3HKO
252 SpA Aerilate Mega Salamence Hyper Voice vs. 68 HP / 180 SpD Mega Gardevoir: 48-57 (31.5 - 37.5%) -- 78.6% chance to 3HKO
68 SpA Ludicolo Hydro Pump vs. 68 HP / 180 SpD Mega Gardevoir in Rain: 64-76 (42.1 - 50%) -- 0.4% chance to 2HKO
252+ SpA Mega Venusaur Sludge Bomb vs. 68 HP / 180 SpD Mega Gardevoir: 110-132 (72.3 - 86.8%) -- guaranteed 2HKO
244+ SpA Mega Charizard Y Heat Wave vs. 68 HP / 180 SpD Mega Gardevoir in Sun: 79-94 (51.9 - 61.8%) -- guaranteed 2HKO
252+ Atk Life Orb Talonflame Brave Bird vs. 68 HP / 84+ Def Mega Gardevoir: 122-146 (80.2 - 96%) -- guaranteed 2HKO
252 Atk Tough Claws Mega Metagross Bullet Punch vs. 68 HP / 84+ Def Mega Gardevoir: 114-134 (75 - 88.1%) -- guaranteed 2HKO
252+ Atk Mawile Iron Head vs. 68 HP / 84+ Def Mega Gardevoir: 132-156 (86.8 - 102.6%) -- 12.5% chance to OHKO
252 Atk Life Orb Terrakion Stone Edge vs. 68 HP / 84+ Def Mega Gardevoir: 126-149 (82.8 - 98%) -- guaranteed 2HKO
252 Atk Landorus-T Earthquake vs. 68 HP / 84+ Def Mega Gardevoir: 79-94 (51.9 - 61.8%) -- guaranteed 2HKO
252+ Atk Bisharp Sucker Punch vs. 68 HP / 84+ Def Mega Gardevoir: 84-100 (55.2 - 65.7%) -- guaranteed 2HKO


Red Zone:

252+ SpA Adaptability Mega Lucario Flash Cannon vs. 68 HP / 180 SpD Mega Gardevoir: 144-172 (94.7 - 113.1%) -- 75% chance to OHKO
252+ Atk Choice Band Talonflame Brave Bird vs. 68 HP / 84+ Def Mega Gardevoir: 142-168 (93.4 - 110.5%) -- 56.3% chance to OHKO
252 Atk Tough Claws Mega Metagross Meteor Mash vs. 68 HP / 84+ Def Mega Gardevoir: 254-302 (167.1 - 198.6%) -- guaranteed OHKO
252+ Atk Aerilate Mega Salamence Return vs. 68 HP / 84+ Def Mega Gardevoir: 154-183 (101.3 - 120.3%) -- guaranteed OHKO
252+ Atk Bisharp Iron Head vs. 68 HP / 84+ Def Mega Gardevoir: 168-200 (110.5 - 131.5%) -- guaranteed OHKO

Speed Investments to jump fully invested positive nature base 70s.