Inside Out

In the Korean comments

One comment reads, in translation, “I can’t even notice the challenge; all I see is that seriously insanely handsome face.” It gives viewers a specific second-watch cue: the performers’ faces were more attention-grabbing to that commenter than the challenge itself.

What the words mean

개잘생긴 (gae-jalsaenggin, literally “dog-handsome”) does not involve an animal. The slang prefix 개 (gae, a coarse intensifier meaning "extremely")- (gae-, literally “dog-”) works as a forceful intensifier here, making the phrase closer to “insanely handsome”; it is emphatic, casual and coarse. The commenter stretches the sound further in 진심개애애잘생김 (jinsim gae-a-ae jalsaenggim, “seriously, so incredibly handsome”) for exaggerated emphasis.