No idea if this set actually works, but I'll give it a shot.

Give, Take, then Punish

- Punishment
- Swagger
- Flatter/Knock Off/Roost
- Psych Up

Item: Leftovers
Ability: Overcoat
EVs and Nature: 170 Atk/170 Def/170 SpDef; Adamant (+Atk, -SpAtk)

Basically, you use Swagger/Flatter as many times as you want, Psych Up (when using Swagger), and then Punishment. Unless you're afraid of the opponent's Pokemon getting dangerously high Attack, you're going to be using Swagger more often, so Knock Off can replace Flatter to make Mandibuzz more versatile, or Roost can takes its place to make Mandibuzz stay on the field a little longer. Also, if you want to be a little bit more defensive or offensive minded, you could put more EVs in that respective stat, but I prefer an equal balance.