How hot is hot?

Hot is a relative term. Unlike cold where we have an absolute number (-274^oC) below which things cannot get colder as it is absolute zero where all molecular motion ends, the top end of the "hot" scale is open.
We do know that scientists have produced superheated gas exceeding temperatures of 2 billion degrees centigrade. That exceeds the interior of our Sun, which is about 15 million degrees centigrade.
Calculations indicate that within a hundred of a second of the Big bang the temperature of the Universe had cooled to 100 billion degrees centigrade. but earlier than this the temperature was higher.
So the hottest hot can be assumed to be >>100 billion centigrade and the coldest cold -273 degrees centigrade.
This puts us and everything we've ever thought of as being pretty much on the chilly side as far as the overall Universe is concerned.
However hot is a relative term. In our day to day life the hottest thing we are likely to experience directly as the flame of an oxyacetylene torch (3200 °C to 3500 °C). This is hot enough to melt steel. A light bulb filament is about the same temperature by comparison.
We can be badly burnt by much lower temperatures. Anything close to 100^o C (the temperature of water) will cause is to suffer cellular injury and potentially death. Hot frypans at 200oC will cause immediate deep burns.
Soups and coffees generally are too hot to drink at 180^oC and pizza damages the inside of your mouth about the same temperature.