I didn't know where else to put this as there was a warning of posts on the trophy guide resulting in infractions, but I wanted to put this somewhere so most people can see it. The glitch happens on the quest "Blood's Honor".
After you return from taking the head of one of the witches back to the Jorrvaskr, you'll find out that the Silver Hand has attacked and killed Kodlak. After Vikas speaks to you, the quest ends, and this is where the quest "Purity of Revenge" should start. If it has glitched, it won't start, and the characters will continue to mourn. The reason for the glitch seems to be having another misc. quest activated for where "Purity of Revenge" takes place, Driftshade Refuge. The quest is one for the Jarl of Winterhold, to get back the crown of winterhold. I myself lost a couple hours of play time, but I hope to ensure people don't lose any. Just make sure you have completed the quest or even better, not even started it. If you are like me and had to reload, I completed the quest and didn't kill anyone just to be safe, and then started the "Blood's honor" quest immediately after, and it worked just fine, got the final trophy in the questline to pop. Hope this helps.