What dangling plot thread would you kill to see resolved?S

Science fiction and fantasy thrive on unanswered questions and strange riddles. And sometimes, going down the rabbit hole can be fun in its own right. But sometimes, you just never get the resolution you desperately crave. What's the most annoying unresolved plot thread in science fiction and fantasy?

Please include a picture or clip so we can see what's been bugging you. Thanks!