When your opponent never parries, for maximum damage use Heavy Melee -Shoot - Heavy Melee
It doesn't work with standard melee.When unstoppable you cannot be parried-Like Abrams' Lvl 3 Seismic impact(4).You can cancel a melee attack with your Siphon Life(1)
Force a parry and hit them after.Intentionally missing your heavy punch works as well, it's more difficult the closer to them you are
If you are being parried after a shoulder charge, get duration extender (Extends stun time, and shoulder charge distance).Debuff reducer will reduce the length of a parry stun.