2001 Mariners: Hold the record for MLB wins in a regular season (116-46), lost in the ALCS
2007 NE Patriots: Hold the record for NFL wins in a regular season (17-0), lost in the SB
2015 Golden State Warriors: Hold the record for NBA wins in a regular season (73-9), lost in the NBA Finals
1995 Detroit Red Wings (62-13-7), 2018 Tampa Bay Lightning (62-16-4): Tied for the record for NHL wins in a regular season, lost in the WCF and 1st round respectively
I know it's not cause = effect and all that, but it's still wild to think about