Of all the vegetables in the traditional Korean diet, godeulbbaegi (고들빼기, Crepidiastrum sonchifolium) is the most intensely bitter.
Tagbitter
Recipe: Godeulbbaegi muchim (godeulbbaegi blanched salad)
Godeulbbaegi’s bitterness is tempered when blanched and dressed with doenjang.
Doraji: A bittersweet root
There’s an old song in Korean about doraji (도라지, bellflower root).