This is completed for completing the Man-Bat most wanted side mission. It is composed of a few parts.
Poking around online, I saw lots of people were getting success at triggering the creature by grappling up to the top of the movie screen opposite the Grand Avenue station tower. It should have dancing movie theater refreshments or the old-fashioned 3-2-1 countdown.
The first is automatic as Batman is attacked by Man-Bat and the player draws the creature's blood.
The second step is after Alfred has identified the blood and sends you to the lab belonging to Dr. Langstrom. You can skip watching the video inside the lab, but be sure to check on the woman and then move to the computer to synthesize the antidote. To do this, you will need to manipulate the
in time with the DNA sequences in order to reach 100%.
This section is somewhat difficult, but whenever there is a discoloration on the DNA strands, you will need to flip the appropriate thumb stick (human DNA is the
, bat DNA is the
). Once you've sequenced it to 100%, you'll have passed that segment.
The strategy for the third and the fourth is exactly the same, but the chances to do this only come after you progress in the main story (I reached the fourth and final segment of the side mission after completing 70% of the main story). It requires you to glide around Gotham and pay attention to the radar transmissions to track down the creature. You will have to do this twice.
This gives you a direction/distance towards Man-Bat, and using detective vision
will highlight the creature in red. Then you just have to follow after it, line up on top of it, and then dive bomb down to get close enough to trigger the cutscene where Batman injects Man-Bat with the serum.
After taking the creature to lockup at the GCPD — the drive of which is made difficult by it rattling around in the back of the Batmobile and sending you bouncing around on the road — the achievement will pop.