In Lord of the Flies,
As his actions in Chapters 9 and 10 show, Jack is clearly power hungry. Does his desire for power contradict any evidence connecting him to "the ethical nature of the individual," or can his dictatorial leadership co-exist with his promoting "fun" and "the individual"?
I think the answer to both of your questions is "no." I don't see much evidence of Jack being ethical at all. He's a power hungry sadist. I think the only reason he is as "ethical" as he is in the beginning of the novel, is because he is biding his time until he has enough "votes" or "followers" to take over the power from Ralph. I think Jack is manipulative, smart, and "dark" enough to take the power from Ralph in whatever way works. He doesn't have to do it through killing like Roger, but he could if necessary.
I don't think of Jack as personally promoting fun and the individual either. I'm sure the argument can be made that states that is how he was able to gain power over so many kids while on the island. I think Jack used that methodology because it happened to work. I truly believe that if Jack saw that fun and individual freedom wasn't working to gain him the power that he sought, then he would shift to a different methodology. Bribery, blackmail, violence, whatever. As a dictator, he cares about control. He doesn't care how he has the control, just that he has it and it's working.