Mega Vanilluxe
Come on, admit it, the ice cream isn't the WORST Pokemon idea.
Regular stats:
HP: 71
Atk: 95
Def: 85
SpA: 110
SpD: 95
Spe: 79
BST: 535
Abilities : Ice Body, Weak Armor.
Mega Vanilluxe:
HP: 71
Atk: 115
Def: 100
SpA: 140 (is it just me or do most of my Mega ideas have either Special or Physical attack power as 140?)
SpD: 110
Spd: 99
BST: 635
HP + 0
Atk + 20
Def + 15
SpA + 30
SpD + 15
Spd + 20
Type change: Ice/Ghost
Ability: Cursed Body
Gained move(s): Shadow Ball, Scald, Ice Burn
Two-turn moves aren't exactly commonly used on competitive teams, but think about the power that Mega Vanilluxe would do. Also, the two-turn effect would make up for the overpowerness
Getting a critical hit with that Ice Burn could do some nice damage. Cursed Body because wynaut? I can easily imagine Vanilluxe being Ghost and having Cursed Body.