The highest temperature recorded on our planet is 5.5 trillion Kelvin. Or 5.5 trillion degrees celsius. The units don’t even matter at this temperature. In 2012, physicists at CERN used the Large Hadron Collider to smash two proton beams containing trillions of protons at nearly the speed of light and generated temperatures up to 5.5 trillion Kelvin (or degree Celsius). To compare, the temperature at the center of the Sun is 15,000,000 degrees Celsius.
The record was merely a side achievement. The scientists at the LHC were/are actually studying a state of matter that existed milliseconds after the Big Bang. They are doing this in an attempt to understand more about the beginnings of our universe and how states of matter, that we are generally aware of, came into existence. The experiment (called ALICE), created this state, which is called Quark Gluon Plasma, where quarks are the building blocks of neutrons and protons, and Gluons are the particles that are responsible for the force between these quarks.
Normal plasma is when you have heated things to an extent where they go from being gasses to a mixture of electrons and protons, like on the surface of the sun. Quark Gluon Plasma is a level higher where you have crazy amounts of energy and have heated stuff to a point where the neutrons and protons break down into individual quarks.