This has a little more to it than the other DLC packs.
There three side missions needed:
1) Screwball chase
- Screwball's side mission becomes available after you've completed all the challenges she has ready for you. Complete them all to at least spectacula for a seperate trophy.
2) Scales of Justice is a collectible mission that unlocks towards the end of the DLC. It requires you to collect tapes of an investigation into the Magia, then talk to an old friend before the trophy pops
3) Humanitarian Aid is also an side quest. This unlocks the bases available for the DLC, which you need to complete to unlock the side mission.
You need to also complete 5 Hammerhead crimes in 5 districts to conolete the 100%
The main missions are obviously needed to get the 100% too.