As of my training data (2021), the Carolina Reaper is considered one of the hottest peppers in the world, with a heat level of over 2 million Scoville units. It is currently the Guinness World Record holder for the hottest pepper.
However, it's important to note that new hybrid peppers are constantly being developed and new records are being set, so it is possible that there may be peppers that are hotter than the Carolina Reaper in the future. It is also possible that there are peppers that are as hot or even hotter than the Carolina Reaper that have not yet been widely recognized or studied.