Eli Cohen

Though he was initially successful, Cohen's activity became increasingly risky and he expressed a sense of impending danger to Mossad in 1964. A year later, his true allegiance was uncovered by Syrian intelligence and he was convicted by the Syrian government under pre-war martial law. After being sentenced to death, he was publicly hanged in Damascus in May 1965. The incident contributed to the sharp escalation of hostilities between Israel and Syria just before the 1967 Arab–Israeli War.
Cohen is highly regarded in Israel, with several streets and roads being named after him. Provided by Wikipedia