Easy gestalt achievement that can be easily skipped.
Iron(ic) Defeat Achievement Guide
- Finished off Project Gestalt with a taste of his own medicine.
You have to be on The Rush (the last level), do it on any difficulty you wish, just do everything to get to kill Gestalt until you have to explode his head with C4.
When you explode Gestalts head, two of his tusks will fly off and you can pick one up. Pick a tusk up and start bashing him till he is dead, do NOT throw it though, last time I did that the achievement didn’t pop up. I suggest commanding your teammates to go away as they might mess up getting the achievement (im not quite sure though so dont count on that).
Once Gestalt is dead by your last tusk punch, you should get the achievement.