I am the lord of the abyss (betrayed/cheated Issei dxd x Knull)

Love can turn to hate

After defeating Trihexa, A month later Issei finds out his harem betrayed him and going out with their new perfect boyfriends then even bad mouthing him behind his back after everything that he had done for them. They turning their back on him

After Issei went missing Rias etc started to realize what have they done and regretting their action but when they reunited once more Issei is not the same as he used to be, a pervert lucky or unlucky because when he fall to the lowest point of his life. Even go as far as do the suicidal act by remove the devil pieces. After doing That he fall unconscious, fallen into the darkness that when he see the void, the abyss and....Knull

Would Issei be insane after encounter with such being?
Or would he even have a mercy for their souls let find out

(Ok firstly this is not my original work! The original work belongs to Leixein and I got inspiration from The Change of a Dragon by IluLugal. I want to use only the betrayed part because their story is so good i wanted to write something similar. But darker)

ENGLISH IS NOT MY 1ST LANGUAGE SO EXPECT BAD GRAMMAR!