This achievement is story-related and cannot be missed.
When you have fought your way through intensive treatment you will eventually reach the "boss fight" against Harley's goons. The fight is just as simple as every other fight. Just pay attention to the platform that will be electrified. Jump/climb to another platform when you see the indicators for an imminent charge-up.
If you need more help, please refer to the video below:
(video credit: The Medieval Gamer)
Hope this helps you guys!
Any improvements? Please let me know in the comments below!