Vullaby switches in. Worst case, it is hit by Iron Head.
156+ Atk Pawniard Iron Head vs. 116 HP / 0 Def Eviolite Vullaby: 7-10 (28 - 40%) -- 98.9% chance to 3HKO
(7, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 10)
Next, Pawniard follows up with Sucker Punch.
156+ Atk Pawniard Sucker Punch vs. -1 116 HP / 0 Def Eviolite Vullaby: 6-7 (24 - 28%) -- 22.8% chance to 4HKO
(6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7)
Vullaby kills Pawniard with Heat Wave "reliably" enough to move on.
Or if you want Power-Up Punch:
156+ Atk Pawniard Power-Up Punch vs. 116 HP / 0 Def Eviolite Vullaby: 3-4 (12 - 16%) -- possible 7HKO
(3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4)
Follow with Sucker Punch.
+1 156+ Atk Pawniard Sucker Punch vs. -1 116 HP / 0 Def Eviolite Vullaby: 9-11 (36 - 44%) -- guaranteed 3HKO
(9, 9, 9, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10, 11)
Or, if Knock Off is your cup of tea:
+1 156+ Atk Pawniard Knock Off (97.5 BP) vs. 116 HP / 0 Def Eviolite Vullaby: 6-8 (24 - 32%) -- 98% chance to 4HKO
(6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8)
+1 156+ Atk Pawniard Sucker Punch vs. -1 116 HP / 0 Def Eviolite Vullaby: 9-11 (36 - 44%) -- guaranteed 3HKO
(9, 9, 9, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10, 11)