홍어 (Hong-eo) is raw, rotten-tasting, ammonia-smelling, fermented skate fish. Most Koreans who've tried it don't like it, although some love it. I'm not a fan.
I'm also aware of surströmming, which is a Swedish fermented herring that supposedly has the worst smell of any other food in the entire world. So I wanted to know - which food was worse?