You did all the "group" quests, and all the collections? There are quite a few long chains that have collections in them, but are easily 30-50k due to the number of turns ins for just the one quest chain alone.

Or the ones you find such as the quest that starts around where you have to kill taskmasters to free the slaves in Hellfire Penn. Guy in the back asks you to get a key, 10k, free his people, 10k, kill the boss, 10k. Took about 10 minutes or so.