The spiciness of peppers is call pepper pungency. Pepper pungency is based on the Scoville Heat Scale whereas the mildest pepper, bell peppers, have 0 Scoville Heat Units (SHU) and the current Guinness Book of World Records record holder for the spiciest pepper is the Carolina Reaper has a max SHU of 2,200,000.
We consider extra hot peppers as having a SHU rating above 500,001. These peppers are in the super hot pepper category. These are the world's hottest peppers and contain well-known peppers such a Ghost Pepper, Trinidad Scorpion, Bhutlah, and Carolina Reaper. Even the smallest amount of these peppers will cause extreme discomfort, hiccuping, profuse sweating, and an endorphin rush. You should use caution when handling the peppers as any amount on your skin or in your eyes will be very painful. It is always best to start with a small amount of these peppers to gauge how they will affect you.