Can someone give me a certain question? please? I believe it's something like "but he is not love back by nobody" But I'm not sure.
First, lets try to change this sentence to "default" order of words. (Current order is correct, it is just emphasizing one of words)
The subject is "никто" - nobody. Subject should be in the nominative case.
The verb is "не любил" - did not love. It is active case.
The verb has the direct object "его" - him (did not love him)
And there is the adverbial phrase "в ответ" - back.
Но никто не любил его в ответ.
Nobody loved him back.
Russian has one more negation then English in sentences with negative pronouns, such as nobody, nowhere, nothing.
Changing the order of words in Russian emphasizes some of them. It also can be used in poetry.
Но не любил в ответ его никто.
(He loved and cared for a lot of people, but nobody loved him back)