For my palate, the hottest, cleanest, most enticing heat is available in Thai food. Not only can you order it HOT but if it still is not hot enough, there's always those wonderful condiments on the table. My favorite HOT HOT HOT is Tom Yum Goong, that fiery soup with shrimp, mushrooms and lemon grass, that goes down as liquid fire. I also love a green papaya salad hot, and there's a homemade thai chili/braised onion relish that I've only had at homes. The Thai beef salad, (mu su mu neau, I think) can also be wonderful when hot. Not all thai food is hot or even has to be, pad thai, a noodle dish, is simply delicious with no fire at all.
The hot I least like is the New Mexican chili, which is simply hot without much taste. The most lethal hot sauce I ever had, and I love those hot sauce kiosks in the Carribbean, was Dave's Insanity. One minute touch of a toothpick could wipe out your large bowl of chili, not to mention blister everything it touches.