The 26th President of the United States, Teddy Roosevelt, regularly staged boxing matches in the White House and took on anyone he could- including professional boxers.
Thai prisoners are released early if they take part in special kick boxing matches against foreigners.
There was a Jewish boxer named Salamo Arouch imprisoned at Auschwitz. While there, he was forced to fight bouts against other prisoners, the losers of which were sent to the gas chambers or shot. He survived over 2 years and 200 bouts, eventually being released when the camp was liberated.