Bergen is the surprising hilly performance you can come up with for Sagan? Kristoff and Gaviria were in that group...I have listed Sagan with the previous "generation" despite his age. I saw only one performance last year -- at the Giro -- to match his mid-2010s level. The other riders I listed had great years in 2020, in some cases both before and after lockdowns.
Sagan at, say, Richmond level was unbeatable. Sagan 2020 looked distinctly beatable. I'm happy to be proven wrong, the more riders with flair and the talent to back it up, the better. (Edit: It's true, he's not a climber, but he's done pretty well on courses like Bergen where you'd think he might not have been able to survive)
I'll try with Grindelwald 2011, Mur de Peguere 2012, Porto Sant'Elpidio 2013, Meiringen 2013, Mount Baldy 2015, Gap 2015, Fermo 2017 and then Tortoreto 2020.