[ESPN] The NY Knicks are currently up 3-1 in the series against SAS. Teams in NBA Finals history that were up 3-1 have a 37-1 all-time record
Source: https://www.espn.com/nba/story/_/id/40337606/what-biggest-comebacks-nba-finals-history
The comeback was also the biggest comeback in finals history. The second biggest comeback was in 2008 when the Celtics defeated the LA Lakers after trailing by 24 points. The Lakers missed all eight of their 3-point attempts in the second half, as the Celtics took a 3-1 series lead and ultimately won the series in six games.