Hottest thing I've ever tasted was undiluted The Man sauce from Dixie's BBQ [1]. Years ago when I interned at Microsoft, they had the interns try the sauce, since we were all from out of town. Whoever had the most would get tickets for the Seahawks game the next evening.

I figured I'd like it, because at the time I was super into hot foods. At least, I was by my own benighted standards. But my adviser told me to take the smallest amount I could, on a toothpick. I said fine, and boy were they right. It didn't feel hot. It felt like I was cutting my tongue with a knife. It only started feeling hot as an inferno after it had spread out through my mouth.

One of the other guys took a spoonful and put it on a bun and ate it in one bite. Then he proceeded to guzzle several cups of milk, before retiring later to the WC. He won the tickets, but apparently was unable to go because he was still feeling digestively sensitive the next day.

These days I don't really fuck around with super hot food any more.

[1]: https://en.wikipedia.org/wiki/Dixie%27s_BBQ