The New York Yankee's
in the 2005-2006 season, the Pistons had their best record in franchise history 64-18.
The University of Kentucky Wildcats has the best winning record in NCAA history, with a 1876-577-1 record since 1903.
A personal best.
The Michigan Wolverines have the best record of any school in all divisions of college football history.
In Nba the Chicago Bulls went 72-10 one year. That is the best Nba ever.
The best record in the history of the Fort Wayne Wizards is 79-61 (.564) in the 1998 season.
University of Notre Dame
Chicago Bulls 72-10
1927 or 2001