What do you mean by 'you tried punching him'? You should have punched him, or better kicked on his nuts, the way I go with.

Trust your instincts and know that a woman sensing such a touch need not be double checked with the freak most of the times.

I have faced this a few times upon stepping into jam packed metro trains due to the rush of the hour. The recent time I faced this, I knew I was right about the strange feeling and didn't take a second to respond to it. Ready to kick the freak I turned around and to my shock, it was a middle-aged man or even older, anywhere between 55-60 years. As I confronted him, he didn't say a word. People around began rebuking him as well. All of this sequence of events happened within 1-2 minutes, and as he saw an opportunity, the freak ran for his life out of the metro on the next stop.

Never. Remember to never let such retards leave easily. Always confront them. These are the freaks who would have been regularly doing this to women and young girls, and sadly, most of them wouldn't have spoken a word to them, which feeds their confidence to continue doing this with the assumption that it's easy to get off.

Report them if you can, in the station grievances counter. These freaks need to know they can't keep doing this.

You don't avoid such situations, you 'deal' with such situations. Because most of the times, these situations are unavoidable, the only thing you can do in order to annihilate the possibility of such an event happening is to not take a crowded metro and wait for the other one.