The highest temperature ever recorded in the universe occurred shortly after the Big Bang, during the period known as the "primordial plasma" or "quark-gluon plasma." At that time, the universe was extremely hot and dense, with temperatures reaching approximately 10^32 Kelvin (K).
In the present-day universe, the hottest temperatures are found in extreme astrophysical phenomena such as supernova explosions and the cores of active galactic nuclei. However, pinpointing the exact temperature in these environments is challenging, and there is no definitive measurement available.
It's worth noting that temperature is a measure of the average kinetic energy of particles, and extreme conditions in the universe can lead to the breakdown of classical concepts like temperature. In some cases, alternative measures such as energy density or particle energies are used to describe these extreme environments more accurately.