When Pascal asks you to either kill him or erase his memories due to his extreme grief seeing all the children having killed themselves out of fear during the machine attack, blaming himself for teaching them about fear thinking it would help them survive in the future.
And no matter what option you pick, it's still awfully tragic. I chose to erase his memory, thinking at least someone would come out of this alive and continue. But seeing him later picking through the scraps of his former family with no knowledge of what he's doing, selling them to you for some bits, broke my heart...
Nier offers no salvation where there is none to be had.