Is Taco Bell's Diablo Sauce the Hottest available at any Fast Food Restaurant?

Not being a Taco Bell frequenter, I purchased their "Fire" sauce recently thinking it was the hottest thing they had to offer, and was gravely disappointed. Now, I've gotten my hands on a bottle of DIABLO sauce and am hoping it at least brings a respectable burn.
The question I really want to explore is "How hot do fast food sauces get?" Is Diablo the most intense heat you'll ever experience eating at a fast food joint? If you think you've tasted a hotter one, please recommend it in the comments section and I'll try to get my hands on it.