Are you kidding? You’re aware that Israel is only using a very tiny part of its military force against Lebanon, right? I know the media doesn’t portray it as such, but Israel has actually been very surgical in its bombings.
You want to see what open warfare in the Middle East looks like? Go study the Iran/Iraq war. If Israel wanted, it could simply pummel Lebanon back into the stone age, killing hundreds of thousands.
Israel could react to violence in Gaza the way Kuwait dealt with Palestinians - round up hundreds of thousands of them, and simply kick them out of the country. Or it could deal with them the way some Arab countries have dealt with their insurrectionist populations - Saddam killed hundreds of thousands of Shiites and Kurds to quiet them down. He destroyed the entire Marsh Arab culture.
Israel could respond to terrorist bombings by rounding up and executing the terrorist’s entire extended family and friends. That’s also a favorite trick of dictators.
Israel could respond to attacks from Hezbollah by firing missiles at Iran or Syria. Nukes, if it had to.
Israel could send out assassination squads to start picking off leaders of countries antagonistic to them.
Israel could decide to simply annex southern Lebanon, expel the indigenous people, and move in settlers.
Israel could ethnically cleanse every Palestinian from its country and annex Gaza and the West Bank.
Israel hasn’t done these things because A) unlike Iran and Syria, it’s a civilized nation that really wants peace and doesn’t want to kill people it doesn’t have to, and B) because with the U.S. at its back, its very existence is not currently threatened.
Take away the U.S., make Israel’s situation more precarious, give the Arabs around it a little more reason to be aggressive, and suddenly you have a fight for Israel’s very existence. And under those circumstances, Israel will use every tool it has at its disposal to survive - including the 100 to 200 nuclear weapons it is reputed to have. Any country would do the same if faced with annihilation.