The hardest i've come across is actually Russian. Phonetically in English it is:Yekhal gryeka chyeryez ryeku. Vidit gryeka v ryekye rak. Tsunul gryeka ruku v ryeku. Rak zaruku gyeki tsap. Abusive comment hidden. (Show it anyway.)
Yekhal gryeka chyeryez ryeku. Vidit gryeka v ryekye rak. Tsunul gryeka ruku v ryeku. Rak zaruku gyeki tsap.