Worst ending for me:
Master Lee is the ultimate villain. He's really the founder of Songrim. JBY 1.0 is really Jin Seol Ran. He wanted JBY 1.0 to be revived from death by using Naksu. Naksu dies/disappears. Jang Uk asks JBY 1.0 to remove the ice stone from him so he could be with Naksu at long last.
*Though im still holding onto a happy ending in the field of daisies.