Sucker Punch has a power of 80. It has a priority of +1, so it is used before all moves that do not have increased priority. If Sucker Punch's target has selected a physical or special attack and has not yet had a chance to execute its move, Sucker Punch will damage the target; otherwise, Sucker Punch will fail. Sucker Punch only depends on the move the target has selected, and is not affected by any consideration of whether the attack can actually be executed, such as status conditions like sleep or freeze or Abilities like Truant.
This move enables the user to attack first. This move fails if the target is not readying an attack.