The incomplete sentence to be completed is: "Although initial investigations pointed towards him ........"
The use of "Although" indicates a contrast between what is stated in the first part of the sentence and what follows. We are looking for a statement showing a change in direction or the opposite outcome from the initial investigation.
Thus, the best completion for the sentence is "the subsequent events proved that he was innocent" as it provides a contrasting conclusion to the initial suspicion suggested by the investigations.