Determining the absolute "king of cuteness" in K-pop is subjective, as perceptions of cuteness vary widely among fans. However, based on opinions and observations, certain idols are frequently mentioned in discussions about K-pop's cutest members.
One example, from a fan's perspective, is Jungwon of Enhypen.
Jungwon of Enhypen he looked cute to me when I first saw him online but when I saw him irl I can't believe how cuter he is. And it doesn't help when he said that he will be engenes baby forever even when he gets old lol.
While this is a subjective opinion, it highlights that Jungwon is perceived as very cute, especially in person. This perception is further amplified by his interactions with fans.
Ultimately, the "king of cuteness" is in the eye of the beholder, but certain idols, like Jungwon of Enhypen, consistently receive praise for their adorable charms. There's no universally agreed-upon king, but these idols are definitely contenders!