Both Reuven and Yehuda spared Yosef from death. First Reuven suggested that rather than killing Yosef and throwing his body in a pit, they throw him in and leave it to Hashem to kill him. Later, when he was in the pit and sure to die a painful death, Yehuda suggests they spare his life and sell him to the passing caravan. Reuven was considered a hero, while Yehuda is singled out from the rest of the brothers, who didn't show any second thoughts about killing Yosef, and blamed for Yosef's plight. Why?
The Lisitcha Elyon brings from the Ponevezher Rov that there was a big difference between what Yehuda did and what Reuven did. "Reuven," says the pasuk, "saved Yosef, LiHashivo El Aviv, to return him to his father, so that he can continue to learn Torah and thrive at his father's side. Yehuda had no grand ambitions for Yosef other than to spare his life. Yehuda's idea of salvation was to sell him as a slave to Mitzrayim which was the most promiscuous society at the time. Yehuda may have saved Yosef's physical life, but he more than buried any spiritual life that Yosef had in him. This is not called salvation. This is murder."
With understanding, the Ponovezher Rov explains the enigmatic Medrash in Shir HaShirim which says, "HaDudaim Nasnu Reich Zeh Maaseh Reuven; Reuven's saving of Yosef is like frangrant flowers."
"V'Al Pisacheinu Kol Megadim Zeh Ner Chanukah; On our doorstep are delicacies," this is Ner Chanukah. What is the connection between the two? He explains that just like Reuven's saving of Yosef was a salvation of his spiritual life, so, too, Chanukah was a salvation of Bnei Yisrael's spiritual existence, as the Yevanim did not aim to kill us, but rather obliterate our religious practice.