Naruto
Sasuke
Kakashi
Other Jinchurikis
Itachi
Nagato
Tsunade
Madara
Hashirama
Naruto, Kakashi,Sasuke,Itachi,Nagato ...it could go to any of those but it is hard to tell or measure who had more painful experiences.
Naruto
Sasuke
Kakashi
Other Jinchurikis
Itachi
Nagato
Tsunade
Madara
Hashirama
sasuke dont see parents deadSasuke or Naruto. Sasuke saw his parents and his clan killed by his brother who he loved dearly and he had to live through the events for three days straight as a result of Tsukiyomi. Naruto had no parents from birth and the villagers that his parents saved rejected him.