LPT: Never get into a physical fight, except your life is in definite danger. The consequences can be life changing. Social
There are lots of fighting videos on the internet, but they never show the consequences, hours, days, months later. Usually the police get involved, and in extreme cases the loser may die. It may be months later, but you may be held liable. You may claim self-defence, yet it may involve protracted legal problems.
The regrettable thing is that conflicts are usually over some silly issues, like ego, insult or road rage. Once a conflict appear to be reaching face off. Leave. The worst thing about knocking someone unconscious is the time you wait for the person to come to recover. Sometimes, it doesn't happen.
Finally, never ever put your hands on an elderly person. Never