Not of all time, just a recent one, but I'd say Dante from Piofiore. I played his route after Yang's based on Otome Kitten's rec route order and man did his route feel bland in comparison. I liked the guy and felt bad for him in other routes but his route had Lili in the dark about the Key Maiden and the Falzone Family's ties "for her sake" and general communication issues that were so unnecessary for like half of the route that made me roll my eyes, and the playing house part was just boring and cliche as hell.
Funny enough, I actually liked him more as a character in Orlok's bad ending, I love Orlok but damn Dante was seriously twisted for taking Lili by force and knowing that he's loved her since childhood just made it better. Who knows if he still had feelings for her at that point since it's not his route and he was consumed by hatred for Orlok, but if his actual route was the setup after Orlok's bad ending, the whole "keeping her captive in the manor" would be more to my taste. The angst of falling for someone who killed your first love out of revenge for his family would've been peak, but alas, Dante's route was rather vanilla.
I also didn't care for Gilbert but that's also as a character (he didn't catch my eye in other routes either) so it's not like I had any expectations for his route to begin with. For a game about mafias, Dante and Gilbert were the most disappointing.
