The Buffalo Bills.
No team has ever lost 5 Super Bowls. The Buffalo Bill lost 4 consecutive Super Bowls from 1991 - 1994.
The Minnesota VikingsThe Vikes lost Super Bowls IV, VIII, and IX. They also lost Super Bowl XI to become the first team to lose 4 Super Bowls.
The Buffalo Bills played in four straight Super Bowls (XXV, XXVI, XXVII, XXVIII). They lost all four.
Minnesota Vikings
The Minnesota Vikings have gone to four Super Bowls (1969, 1973, 1974, and 1976) and lost all of them. The Buffalo Bills have also lost four Super Bowls except they lost all four in a row (1990, 1991, 1992, 1993).
Buffalo
The Buffalo Bills are the only NFL team to have played in four consecutive Super Bowls and lost (SBs XXV, XXVI, XXVII, and XXVIII). The Minnesota Vikings have also played in four Super Bowls and lost but they were not consecutive (SBs IV, VIII, IX, and XI).
Buffalo not only lost three in a row, they lost four in a row (Super Bowls XXV-XXVIII). Both Denver and Minnesota each lost three out of four (Denver: XXI, XXII, XXIV - Minnesota: VIII, IX, XI).
The Minnesota Vikings, who have never won a Super Bowl despite four appearances lost Super Bowls IV and IX at Tulane Stadium in New Orleans.
Steelers
Pittsburgh steelers
The 49ers.