Quantum Theory

In order to unlock this achievement, you need to defeat the Chariot during the Thorax level which is scene 7, on hard difficulty and in less than 1 minute and 30 seconds. Now, to effectively defeat the Chariot, you need to pump rounds into his chest. This can be a little tricky on hard especially while trying to dodge his attacks and stay within the time frame. Right when the boss battle begins, get a quick shot on him by holding LB and throwing Filena at his chest. Immediately afterwards, power roll past him and make your way to the exit door in the back of the room, stand next to the door so his bullets that he is firing at you hit the wall in front of you. Return fire, preferably with a machine gun. There is plenty of ammo around the room, not to mention a box directly in front of your position at the door. If he moves forward, just do like you did before and roll/sprint past him to the opposite side of the room. In the event you are forced to move to the opposite side, use the columns that he can’t destroy for cover. By this time he should be almost dead if not dead already.

I hope this solution helped! Leave a comment letting me know if there is any room for improvement! Thanks.

Video solution explains and shows everything you need to do.
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