The entirety of Gaza, with however many nukes are necessary to either kill every single person in Gaza or force them to leave. Since Hamas is a political group in charge of a territory, if you nuke the whole territory and leave no one alive in there, you effectively defeat it. Turning a ruler into a small terrorist group is a victory.
Thus why I am saying that retaliation is the driving force behind Israel not doing it.
I see 2 motives for Israel's actions....
1) Vengeance against Hamas.
2) Eliminating Palestinians so Jewish settlers can move in.
I am not saying it is the same in all scenarios. I am saying the ethics are the same in this scenario.
The ethics superficially appear the same only if one
ignores ethics, motives, strategy, & probability of success.
Is it alright to kill civilians, if they are collateral damage, to end a war? If it is, and if Israel isn't even going nuclear, how can we condemn it?
It's a balance of military interests, saving lives of
one's own side, saving lives on the other side,
long term effects, etc.
Nuking Japan arguably saved lives by ending the
war. Note also that conventional bombing to induce
firestorms was deadlier, but couldn't end the war.
The nuclear show of force did so because it inspired
futility of continuing.