it depends on the phrases. I assume that the person talked thinks the indicated person is 눈썹이 짙다 and thinks it either not good looking or annoying.. so it is called 못난이 hope it may help.

~이 refers to the person. [이 이가 어디갔지? = 이 사람이 어디갔지?] In this case, 못난이 means the ugly person because of their bushy eyebrows. But I don't think it's a complete sentence. If I use it in real life, it'd go like this Q: 이 눈썹 정리도구는 누구한테 줄까? A: 눈썹 짙은 못난이에 (= 눈썹 짙은 못난이에게 주는것이 좋겠다.) PS: 못난이 is not an usual term for 'ugly one' though. They would just use 못생긴사람, 못생긴놈, ... etc. Moreover it sounds like somewhat old-fashioned to me. I've never heard of it in spoken language in my entire life. Instead of this, they use the plural form '못난 사람들 / 못난이들' normally. And these mean the ones not just ugly but who don't have riches, who aren't from good families, ...etc. And especially, for the assholes whose minds are ugly.