The first part of the Joker fight is VERY easy. Use standard attacks and counters (Y) at the right time #1. Keep doing it until Joker falls down #2. Luckily that was only an introduction, as now Joker will "invite" his goons to play along.
Before we move on to discussing the enemies, a few words have to be said about the unique difficulty applying to this battlefield. There are two railway tracks, along which train cars will come from time to time #1 and you of course should avoid getting hit by them. An incoming car is always indicated by a flashing red light #2. If you feel up to it, you can wait with evading it till the last moment, thanks to which the enemies won't make it in time and get hit themselves.
The fight begins with, "only" common enemies. As they're in a very numerous group, you have to remember about performing counter attacks often #1. Look out for the ones equipped with firearms #2 and don't let them hit you too often. Also keep an eye on anyone trying to throw anything at you. Joker will also participate in this fight, though he won't be too much of a threat and you can ignore him for the most time.
Unfortunately the thugs will soon be joined by much stronger enemies. The first will be the already known Abramovici #1. Keep away from him, looking out for his strong ground hits #2 and occasional jumps. It's best to leave him for the end.
The second stronger enemy that will join the fight is a Titan #1. In this case you have to look out for his charges #2 and the defeated enemies' bodies that he throws. Depending on your preferences, you can leave the Titan for the end, or jump onto his back sooner (after performing the Super Stun) and therefore have an easier time eliminating the normal goons.
Continue fighting #1, while constantly moving and keeping Batman's health at an reasonable level. Also don't forget about having to dodge the train cars. Your objective is reaching a state in which only Joker, Abramovici and the Titan are left on the battlefield #2.
Abramovici should prove much easier to take care of than the Titan. Stun him with the Electrical Charge #1 and afterwards use Beat down by rhythmically pressing X #2.
As for the infected Titan, you have to run to him after one of his charges and use the Super Stun by pressing B three times #1. Only afterwards should you use the Beat down (X) #2.
In the end you will have to take care of Joker, treating him in the same manner as the enemies equipped with blades #1, i.e. jumping above him or pushing the analog stick backwards while holding down Y. Defeating the lonely Joker won't be hard #2. Watch the new cutscene including Talia al Ghul and Catwoman. The man hero will be forced to stop Protocol 10 from commencing, before he can head after Talia and Joker.