I had a friend who would cook up a spicey beef dish. He simply cut the habeneros peppers with a knife then cut the beef with the same knife. He'd throw the cut peppers away. All the dish needed was the amount of hot that was transferred on the blade of the knife!
I saw some wildly hot concentrates in New Orleans. They had stores that sold many hundreds of varieties. One store had all the names listed and you could taste what you wanted except for 4 of them. These 4 were so hot you had to sign a release of liability before they would let you taste them.
Now that's hot!
Sometimes the odd garden pepper can be much much hotter than its neighbors. Same varieties in the same soil ,off the same plant etc etc but every now and then you got one individual pepper that would take your breath away.