3. Denver Broncos
One team that has been kryptonite to the Pittsburgh Steelers since the NFL merger is the Denver Broncos. The Broncos came around just one decade before the merger, and the Steelers never played them prior to that point.
From 1970 until now, however, this feud has been extremely lopsided. Despite all of their success in the '70s, the Steelers were just 1-5-1 against the Broncos from 1970-1977. From there, wins were still very sporadic, and Denver got the best of them more often than not.
The John Elway era from 1983 to 1998 was not kind to Pittsburgh fans, as the Steelers went just 4-8 over this span against the Broncos. Even after Elway retired, their struggles continued -- particularly when playing at Mile High Stadium. In fact, the Steelers are just 1-5 in their last 6 games in Denver.
Playing the Broncos on the road is always a tough atmosphere, and Pittsburgh has not fared well historically in these matchups. Their cringy record of 13-20-1 (39.7 percent) shows just how much they have struggled with this opponent since first playing them after the merger.