My grandpa was the boxing champion of the US Navy back in the day, and he's always stayed pretty fit since. Well, a few years back he owned some apartments and allowed some manager to live there free of rent in exchange for the general duties of a manager. One day, however, my grandpa found out that the manager was stealing money, tools, and letting his friends live for free in the apartments while turning away possible tenants.
When my grandpa confronted him about it with my grandma, the guy freaked out and started yelling, "are you calling me a liar?" My grandpa (and this is all on video), put his hands up and said, "I just want you to get your things and leave. Don't bother with trying to get the stuff back to me that you took, just leave." At that the guy jumped across the table, grabbed my grandpa, and shoved him against the wall. About 10 seconds later the guy, who was about 25, was on the floor in some pain after a few hooks and an uppercut. The police came and arrested him.
Yeah, my grandpa was in his 70s when it happened, but he still packed a mean punch. He probably still does...