https://en.wikipedia.org/wiki/Dendrocnide_moroides
' The sting is infamously agonizing. Ernie Rider, who was slapped in the face and torso with the foliage in 1963, said "For two or three days the pain was almost unbearable; I couldn’t work or sleep, then it was pretty bad pain for another fortnight or so. The stinging persisted for two years and recurred every time I had a cold shower. ... There's nothing to rival it; it's ten times worse than anything else." '