The Explosive Gel was a gadget (and, on occasion, weapon) that was used in Batman: Arkham Asylum, Batman: Arkham City, Batman: Arkham Origins, and in Batman: Arkham Knight. That gadget was used to break structures and could take down armed and unarmed thugs when used in collaboration with a structurally unsound wall. If a single spray of Explosive Gel was set off on a normal, structurally sound wall, the thug would only be knocked down and be made vulnerable to crouching Takedowns.