I am currently looking at my favorite Pokemon, Grumpig for the VGC format.

[Freezing Dart]

It's Calm, with 182 HP, 252 Def, 72 SpAtt, 4 Spe. It knows Psychic, Power Gem, I don't know what else, If I should try RestTalk and Baton Pass a Calm Mind/Nasty Plot to it or use Calm Mind with something using Heal Pulse. It holds a life orb.

Some calcs

252 Atk Parental Bond Mega Kangaskhan Return vs. 182 HP / 252 Def Grumpig: 130-154 (73 - 86.5%) -- guaranteed 2HKO
(130, 132, 135, 135, 136, 139, 139, 141, 144, 144, 145, 148, 148, 150, 153, 154)

252 Atk Parental Bond Mega Kangaskhan Sucker Punch vs. 182 HP / 252 Def Grumpig: 138-165 (77.5 - 92.6%) -- guaranteed 2HKO
(138, 141, 141, 144, 144, 147, 150, 150, 153, 153, 156, 156, 159, 159, 162, 165)

+2 72 SpA Life Orb Grumpig Psychic vs. 4 HP / 0 SpD Mega Kangaskhan: 133-156 (73.4 - 86.1%) -- guaranteed 2HKO
(133, 133, 134, 136, 138, 140, 140, 142, 144, 146, 148, 148, 149, 152, 153, 156)

+2 72 SpA Life Orb Grumpig Power Gem vs. 4 HP / 0 SpD Talonflame: 421-499 (273.3 - 324%) -- guaranteed OHKO
(421, 426, 432, 437, 442, 447, 452, 458, 463, 468, 473, 478, 484, 489, 494, 499)

252+ Atk Choice Band Talonflame Brave Bird vs. 182 HP / 252 Def Grumpig: 127-150 (71.3 - 84.2%) -- guaranteed 2HKO
(127, 129, 130, 132, 133, 135, 136, 138, 139, 141, 142, 144, 145, 147, 148, 150)

72 SpA Life Orb Grumpig Power Gem vs. 84 HP / 0 SpD Talonflame: 213-255 (129.8 - 155.4%) -- guaranteed OHKO
(213, 218, 218, 224, 224, 229, 229, 234, 234, 239, 239, 244, 244, 250, 250, 255)