The sucker punch.
As I learned working as a bouncer, most fights don’t start with a formal whistle or a referee telling them, “Let’s get it on!”
It is one man swinging his fist hard at the other man’s face without invitation. People who have been in lots of street fights know this.
Many (most?) fights are over after this punch. What we learned was to keep an aggressor at a arm’s length distance. Don’t allow them to be close enough to get a full swing in on you with you being prepared.
Some guys will look relaxed before they swing. Others will be stiff with their hands at their side, or ask you inane questions with the answer not mattering (they are just provoking you effectively).
The big idea is don’t let them near you within swinging range, and just say, “I can’t let you that close to me,” while holding your arm out. If they want to escalate, so be it, but that way you start on more fair terms.
Why? Because a sucker punch comes with your chin exposed. And no matter how tough or strong someone is, we can all be knocked out.
Here is former UFC champion BJ Penn, getting knocked out by a drunk fat guy outside a bar. He left his chin exposed and effectively said, “C’mon hit me.” And he learned a tough lesson.
In short, street fights are highly dangerous and unregulated.
Avoid them at all costs.