Nearer to Bloomfield Road (Blackpool FC) for a start, and I am sure many drinkers will do a pub crawl from South Prom to North town centre as there is more than enough pubs. Rarely see any trouble on the line other than a Friday/Saturday/Bank Holiday weekend though.
The 0350 Brighton-Victoria can be quite lively. I believe there used to be a 0150 but this was stopped due to Anti-Social behaviour?
I wouldn't be surprised if many of the drunks on the Blackpool South line board at Lytham - it's a popular place for the locals on a night out. But unless someone who uses that line regularly knows different I haven't heard much about it being particularly bad for anti-social behaviour.
Most of the aggro in Blackpool is late night / early hours - too late for the trains and more likely to be locals or people staying overnight (or just not going to bed). I've never seen anything other than high spirits on a Blackpool North train but I'm sure things flare up from time to time just as they do anywhere.
Some of the worst travelling experiences for me have been on Saturdays because of football 'fans' (and rugby fans once at Leicester); intimidating behaviour, offensive language, peeing in bottles, and in one case hassling a young woman to tears (that was the rugby fans). I've been waiting for a train at Nottingham and watched police escort the fans to the station then just abandon them; from being escorted by horses it's down to a couple of BTP, railway staff and, of course, the public being left to fend for themselves. I now check all the football fixtures before a Saturday journey!