This achievement is story-related and cannot be missed!
*** Spoiler - click to reveal ***You'll eventually come to Killer Croc's lair and have to pick up different roots to mix an anti-titan compund. As soon as you enter the location with the floating planks walk slowly to not attract attention. Follow the radar because it will lead you to the roots. At some points you'll need your line launcher to get past some gaps between the planks. Whenever croc appears aim for his neck with your batarang and let it fly. He will fall into the sewer and you are good to go. Every now and then he will start to shake the planks from below. Just keep running until these sequences end. When you have picked up all the roots you need to escape the lair. At some point an escape sequence will start and at the end of it you will find yourself at the starting point of his lair. Just wait for him to step on the brittle floor and activate your explosives. The achievement will unlock after the cut scene.
(Video credit: Batman Arkham Videos)
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