I'm a guy, I generally agree with /u/makeitquick42 too. I think /u/throwaway452413 would be making a target out of herself by following that advice.

I think OP unfortunately finds herself in dangerous circumstances, being frequently around people who evidently do pose a threat. Obviously it would be nice if she can avoid the subway all together but it doesn't sound possible at this point.

There's so much in here about pepper spray and weapons and all this stuff - and it all has a place but she really needs to work to not get to that point. If she's at the point where she's pepper-spraying someone, a lot has already gone wrong and really it comes down to 'hope' at that point. I think the best she can do is to put in a preventative effort to avoid getting into a confrontation - because confrontations can be incredibly stressful and unpredictable and any sort of 'training' or wits tend to go out the window if she really becomes scared and has a lot of adrenaline going.

I think she needs to ride the train without any headphones, be very aware of who's around her, and move to another train car when she feels uncomfortable -- I think trying to get out of a bad situation is much safer and more practical than trying to fight an aggressive misogynist.

Being alone puts her at a much increased risk of being victimized. I think she should try to make buddies with people she feels safer - the 'buddy-system' in general should be utilized as much as she can. It sounds like it might be outside her comfort zone to ask strangers to sit with her or walk with her down the street but I think it's more practical and implementable than the post I'm referring to. Telling almost any normal-seeming person, "I feel uncomfortable sitting alone on this subway, can I sit with you?" will get her support. She's also presumably going to be seeing the same people frequently given she's on a commuting schedule.

I think those steps can be implemented right away and are within what anyone can practically do. If that fails and she does feel like she's being victimized, I think she needs to try to get away as soon as she can (as opposed to sitting there and politely engaging) - get off at the next stop, start calling for help if she feels 'stuck'. I think fighting is the absolute last measure.