What key middle eastern leader took a moderate approach toward israel, which ended up costing him his life?

President Anwar Sadat of Egypt had worked together with Israel's prime minister Menachem Begin, at the urging of US President Jimmy Carter.  They met at Camp David in the US for 12 days in September of 1978, and worked out the Camp David Accords.  Egypt and Israel later signed the Egypt-Israel Peace Treaty in March of 1979 -- a peace between Egypt and Israel that has lasted to the present day.

Sadat, however, paid a price for his peace efforts.  Islamist activists in Egypt heatedly opposed him because of his moderation.  Sadat was assassinated in October, 1981.

Militarism is the answer.