(Missable) This one is kind of hard because it’s so unclear, but once you know what the “environmental object” is, it’s not a problem. Ok, so the unarmed thug and the armed thug, you’ll find plenty of in the course of the DLC. The Titan is found towards the end after clearing out the dry dock and before rescuing Batman.
The environmental object is kind of hidden. After you regain control of Robin, you’ll go through a fight, go through a grate to get past a malfunctioning door, and end up confronted with a sniper. When you have the bullet shield up, go through the vent to your right and you’ll come out in a little room with an assembly line on the other side of the room. Attach the Snap Flash to one of these, and when it gets behind the sniper, detonate it.
Note: This needs to be done all in one playthrough. If you get three, but miss the environmental object for example, you’ll need to play all the way through the Titan to get this.