Contested succession or political election situation. Give the candidates qualities that appeal to and are disliked by different party members. Expect them to put themselves forward as 3rd party candidates so have a plan for that.
Hostage situation
Curse then with something that needs wish to solve. I'm running The Scriveners Tale from Candlekeep Mysteries right now and it's the most heartburn my level 14 party has had in a long time.
World ending shit where they can't (or probably can't) stop everything bad from happening. Make them choose to save the city or their favored NPC.
They've basically turned into superman by the time they're 3rd or 4th tier so hit them with the line of stuff that makes for interesting superman stories.