Dispose the snipers first outside of the steel mill. Take note that the Disruptor can deactivate the guns of the enemies. Always take out the guards one by one. You have to isolate them so you will not get frustrated trying to deal with multiple guys especially the ones wielding firearms. Use the explosive gels on walls to provide misdirection, after the explosion quickly move to another area and ambush the incoming enemy as you prefer to. Use your jammer at the start and disarm as many enemies as you can first while being perched above, then focus on the other guys who still have dangerous firearms first. Also use the multiple batarangs for multiple knockdowns leading to multiple knockouts. After beating the guards, enter the left entrance, then go up. Enter the grate and drop down on the guards below. Then use the computer station at the corner afterwards. Activate the door and crack some codes. Once upstairs. Open up the weak wall and face the Enforcer sub-boss and his minions. FIght normally and use cape stuns for the enforcer himself. Follow the video guide below:
After beating them, turn on the crane device using the switch to crack the wall, then pull it back using the Batclaw and let go to open it up completely. Enter the opening afterwards. Utilize the Evidence Scanner on the body inside the elevator, then enter the door. Crack another code then go inside the door. For this Predator room, just use the usual isolation of enemies and take out everyone one enemy at a time. Use the explosive gels on walls to provide misdirection, after the explosion quickly move to another area and ambush the incoming enemy as you prefer to. Use your jammer at the start and disarm as many enemies as you can first while being perched above, then focus on the other guys who still have dangerous firearms first. Enter the office once you're done. Again, use the Evidence scanner to investigate the venom and follow the trail at the ceiling. Backtrack to the front gate of the steel mill.