Rattlesnake Bill's eliminiment
A medicated topical preparation that's purportedly intended to soothe muscle-pain/stiffness, but is so horrendously powerful/concentrated (think, the searingly-strong stuff that Laurel Jr. spilled onto Hardy Jr.'s behind after accidentally shooting him with the BB gun in the movie "Brats", with predictably hysterical-screaming-and-writhing results) that the unfortunate user of said concoction actually feels like it's murdering ("eliminating") him.
Perhaps Achmed didn't get his flesh removed by the "premature detonation" of his suicide-bomb --- on the show, it is stated that Achmed's son AJ had "sent him a bottle of skin-lotion" as a gift, so maybe it was actually Rattlesnake Bill's eliminiment, and it literally dissolved the flesh right off him. It's no wonder, then, that the resentful Achmed later contemptuously "sent him back half a bottle", and that AJ now looks largely "skeletonized", just like his body-less dad... probably HE tried some of the eliminiment on HIMSELF, with similarly-horrific results.