alt Hacker NewsLearning how to throw a punch isn't that much work and gives you a huge multiple on power output.
Also throwing a bare knuckle punch against someone's head has a large likelihood of the puncher breaking multiple bones, though depending on the outcome that may be preferable to other alternatives.
Most people tend to punch with a loose hand to the top of the head: this simultaneously increases the chance of breaking their hand; reduces the impact force; and, strikes one of the most insensitive & hardest parts of the body (the skull). Trained fighters are targeting an untucked chin with a short high acceleration punch (jab, uppercut), with a tight fist. It is technically very challenging to do this, even for professionals.
In general: use your sneakers; if necessary, push opponents away with with your palms and tightly held fingers.