losingest
los ing est |ˈlo͞oziNGist ˈluzɪŋɪst | ▶adjective informal losing more often than others of its kind; least successful.
losingest |ˈluːzɪŋɪst | ▶adjective N. Amer. informal losing more often than others of its kind; least successful: the losingest club in baseball history.