losingest

los·ing·est

 (lo͞o′zĭng-ĭst)
adj. Slang
Less successful or losing more often than any others of its kind: "help turn around one of the network's losingest nights of the week" (Washington Post).
References in periodicals archive ?
Even the losingest team in Celtics history, the 15-67 squad of 1996-97 that somehow didn't result in the Boston landing Spurs center Tim Duncan in the NBA Draft managed to go 4-10 in November.
champion Philadelphia Phillies in the LCS--the latter matchup presenting an interesting juxtaposition, as the Giants are baseball's winningest franchise while the Phils are its losingest. While this is the Giants' only championship (so far) in San Francisco, it certainly is not the franchise's first brush with greatness.
In addition, NFL clubs have revenue-sharing, which means that even the losingest, weakest teams like the Detroit Lions receive a huge windfall every year, even if they don't win a game.
Even his promoter, Don King, called him "the winningest, losingest fighter I have ever seen" yesterday.
"Cedric the Coach" would feature the comic thesp as the assistant coach of the losingest team in the NBA, who suddenly finds himself elevated to the role of head coach.