For korean dramas - Not bad hair, but I just don't like those hairstyle with heavy bangs over the forehead for guys, and especially for older men (just check the hairstyle of ML in Gentleman's Dignity lol).
Then for the women, also those hairstyle with the bangs over the forehead, but the bangs are soooo thin. I get it's a popular style, but I personally am just not a fan.
I think part of the reason I like Stranger/Secret forest, is that ALL the men in that show had their hair parted nicely (because they're prosecutors lol)
For Japanese dramas - long, uncut hair for men (like most younger MLs), and over style-ized hair (like the later seasons of Gokusen), that it looks anime-ish