"Sad but hilarious" is "웃픈"(ut-pŭn) in Korean.
웃픈 means 웃기다 (Ut gi da), and also means 슬프다 (sad), it is the compound word of both words. It is an expression that is used when it is called the "do not laugh but, sad but I laugh like, cry". It is often used on the Internet.