i always thoiught he was somehow related to dumbledore. but the first question i think that voldemort is a great wizard and even though he didn't die he lost his body which is like dieing and what happened to him is probably worst than death itself.

and remember in the end of the fifth book when dumbledore was deuiling with voldemort he told him that death is not the worst thing and voldemort said that there is no such thing worst than death so maybe that is why dumbledore didn't kill him because there is something worst than death . but what is it ?

just a thought