So this isn't so much a guide to the acheivement as the acheivement is based on progression and should have unlocked already at this scene, however it is the solution to what i thought was a bug preventing you from intereacting with one of the Rufus clones.
I spent a fair bit of time pressing the A and X buttons on all 3 Rufus' and would only get dialogue when interacting with Left and Right, and i thought this was a bug but now i think its part of the game's design.
To solve this puzzle you need to press Down on the d-pad to actually look inside your iventory, close the inventory and press X (the look option) on a different Rufus. This promts a new dialogue introducing a new interface.
Next you need to cycle through each Rufus until you find the Acid (Blue Rufus/ Right), Press X to Inspect the Acid. Next, close the inventory and use the acid on Middle Rufus so that they fight over it.
Use the new Interface (RT) to select Green Rufus (Left) and Pick Up the Acid from the other two.
Hope this helps anyone else stuck at this point