You could have the object/attacker alter its course for the bullet behavior when it is close to a given object/target.
Perhaps measure the distance, and if it is within certain distance, set an instance variable to the opposite angle, and lerp the bullets angle of motion towards the newly set opposite angle (variable).
event
distance(attacker.X,attacker.Y,target.X,target.Y) < 100
sub event
trigger once
set var oppositeangle = angle(attacker.X,attacker.Y,target.X,target.Y) - 180
sub event
set attacker.bullet.angleofmotion = lerp(self.bullet.angleofmotion, self.oppositeangle, 10*dt)