8.The manner in which the execution was discussed was handled inappropriately by the joking relatives of the deceased.

Ans.

8.The joking relatives of the deceased inappropriately handled the manner in which they discussed the execution.

Here you have two passive voice constructions. The first one is embedded in the relative clause "in which the execution was discussed." Here the agent is hidden, but presumably the agent is the same joking relatives of the deceased.

The other passive voice construction is in the main clause. Here the agent of action is again the joking relatives of the deceased.They inappropriately handled the manner . . .