Ummm... I would pick Goong or Princess Hours.
It was just.... HUH?! The whole plot was great but I found myself unable to finished it. I mean, I've finished it by skipping A LOT of BORING episodes. The ending was soooooo predicted.
Second, The Moon That Embraces The Sun
The first 5 episodes (which are played by the teen actors) were soooooo great.... But starting ep 7 or 8... No matter how much I've tried to think that Ga In is Wol/Yeon Woo, it just doesn't match at all with the child actor. And Kim So Hyun as a king?! The whole ending really pissed me off. I mean, the ending was soooo classic. The evil dies, the main leads win, the end.
So Much 'meh' feeling there..