Attack on Titan 2

When a comrade needs saving, you will see a red circle with the character’s face appear on the screen. The outside of the circle will show you how much time you have to save them.
Normally you will see the person in the hand of the Titan when you get close, but sometimes they will be harder to spot if they are caught in its mouth.
Either way, it doesn’t matter where you attack the Titan. As long as it receives damage, it will drop your comrade.
This counts for any npc, including in your squad. Just repeat this 100 times and the achievement will unlock.