RoboCop: Rogue City

At the end of every main mission, you'll either automatically end up in your caged room in the police station or you'll be told to head there. You'll then get scored on your performance for the mission. You score is based on:
 

• Completing all main missions (no way to avoid this)
• Completing each side mission
• Collecting crime evidence (this is the Incriminating Documents, Stolen Wallets, etc., that you find all over the place)
• Discovering secrets
• Doing optional objectives

At the end of each mission, you'll be shown a tally of these items and then be given a score. For this achievement, you need to get an 'A' on any of these.

Personally, I got an 'A' on the first two missions with no guide and without trying. The first mission is by far the easiest, since there are no side missions. I posted a clip below showing my rating for the first mission. 

https://www.xbox.com/play/media/n29BiDqb7W

I have no idea what those two secrets are that I apparently found, but I'm going to guess that one was the person overdosing in the basement (since you can scan them), and the other was the stash of anti-depressants I found later on, on the top floor, right before you do your first breach. You can see the optional objectives there to save the hostages in each of the two breaches. I failed the second one (I saw one hostage get shot) and still got an 'A' rating, as you can see in the clip, so you don't need to be perfect. But, if you're concerned you missed something else or didn't find enough crime evidence, you can reload your checkpoint if a hostage dies to ensure you complete both of those objectives.