Transformers: Rise of the Dark Spark Tread Lightly can be unlocked while playing as Grimlock, and at the end of Chapter 13: Extinction.
For this specific achievement, you have to protect Optimus while he is trying to open a door and escape Downtown.
Thread Lightly can be a tricky achievement/trophy because you are asked to prevent Optimus from falling below 50% health. In other words, your goal is to defeat waves of enemies as fast as possible.
The Decepticons spawn from three directions, so make sure you stay mobile and move around. If you run low on health, try to execute your enemies, and don’t forget to keep your shield up.
Tip: Don’t switch to the dinosaur form because you will move slower, even if you inflict more damage. The achievement/trophy can also be unlocked on Easy difficulty.
Achievement/Trophy Requirement: “As Grimlock, prevent Optimus from falling below 50% health while defending him.”
