The correct option is
C He did not like his parents, nevertheless, they showered love on him.
Sometimes conjunctions combine two sentences, which are not related and the second sentence contains an opposing idea which the reader does not expect. Such conjunctions are called concessional conjunctions. Examples are: Nevertheless, nonetheless, despite, even though, although, etc.
In the given example: The two ideas sentences contrast each other. If he did not like his parents, it is expected that they reciprocate and do not love him. But, they showered love on him. Hence, in such a case, we have to use a concessional conjunction. Option B is correct because "nevertheless" is a concessional conjunction.
Option A: "As soon as" is a conjunction used to join two actions/events, which happen one after the other, almost immediately. i.e At the very moment one action/event is completed, the other one happens. In the given example, the two sentences are not related by time in this manner. Hence, option A is incorrect.
Options C and D: “As a result” and "so" are conjunctions which are used to indicate cause-and-effect relationships. They are used when one sentence is the cause of another. Here, one sentence is not the cause of the other. Hence, these conjunctions cannot be used.These two options are incorrect.