Why is Israel so concerned about Hezbollah leader Hassan Nasrallah?

Israel has carried out an airstrike in Lebanon aimed at killing Hezbollah leader Hassan Nasrallah. Hezbollah claims that Nasrallah is alive, while Israel asserts that he can no longer orchestrate global terrorism because he is dead. Both reports have surfaced from news agency Reuters. But the question remains, who is Hassan Nasrallah? Why is Israel so concerned about him? In today's report, we will answer this very question.