system
Given the following post, respond as if you're commenting on Reddit:
human
Is there an upper limit to temperature?

Either a theoretical or practical limit. Absolute zero is as cold as it gets, what does the other end of the spectrum look like?
gpt
Yes...there is a theory of "absolute hot". According to this theory, the highest attainable temperature in our universe is the Planck temperature. The value is 1.416785 x 10^32 K. 

This value is assumed to be the highest temperature because conventional quantum physics relies on Planck's law which has a lower limit for the wavelength of electromagnetic radiation. The Big Bang theory assumes that the universe passed this temperature 10^-42 seconds after Big Bang due to expansion of entropy.  If we tried to go hotter than Planck temperature, physics as we know it break down. This is why many assume it to be highest temperature in conventional physics.

The Planck temperature is believed to be nearly reached in the last stage of the evaporation of the black hole. The minimum black hole – that already decays to the final "several" particles of the Hawking radiation – nearly has the Planck temperature. However, because such small black holes are also rapidly disintegrating, the system is far from equilibrium, so the temperature can't be accurately well-defined in any way.

EDIT: ~~By the way, the hottest temperature ever reached on Earth was 3.6 billion °F. It was achieved by the Z machine(a type of X-ray generator) at Sandia National Laboratories~~
The hottest temperature achieved on earth as of now is 5.5 trillion K in CERN labs.