"Colonel Charles Moreau was a French soldier serving in the artillery and an officer of the French Legion of honor. He achieved the worst result ever recorded in an international chess tournament by losing all his 26 games in the 1903 Monte Carlo tournament."
We have some data at least...
But the worse player can also be desleal one, one that do not respect the oponent, a person withou ethics and so on.
I found this video about chess worst looser.