The Invincible Body, Fighting an Iron Devil is an achievement/trophy in Deus Ex: Mankind Divided. It is awarded for using the Titan Shield to protect yourself against an explosion.
Tactics
The Titan Shield augmentation is required for this achievement. Once you see an enemy grenade in your vicinity, activate the Titan Shield and move close to it. When it explodes you should get the achievement.
A good place to be awarded it is in Otar Botkoveli's underground casino. Once the Dvali are hostile, run upstairs to Otar's office. Rather than entering the room after you, the enemies should instead throw a grenade into the room. Run towards it and activate Titan Shield, getting you the achievement.