Two bouncers knock out two people with punches, slaps

Excessive force on behalf of the bouncers, and idiocy on behalf of the drunks who initiated with aggressive posturing and continued to approach after it was obvious they were outmatched.

The first bouncer kicks his downed opponent in the groin after he falls. The second slaps him down again when he gets up and refuses to leave. A friend attempts to intervene and is punched.

Shop owner lays counter-ambush on robbers

The robbers started this with an advantage of initiative, numbers, preparation and mental preparedness. This is why the ambush is the most effective form of attack. If the shop owner were to react at this time, he would lose the majority of the time.

This shop owner feigns submission, waiting until the robbers are no longer focused on him and draws to fire when they are at their most vulnerable. This is a counter-ambush.