I know the lowest possible temperature in nature is 0 K although we have been able to only getting ever closer and closer to it but not at 0 K.
But on the opposite spectrum of temperature, what is the highest that is achievable naturally or artificially? Is chemistry still relevant at this temperature as we know it or is it senseless to think of any typical reaction to take place.
My best guess is plasma followed by nuclear fusion as it creates heavier elements but I am not certain.