If Israel has a nuclear arsenal, why has not used its against Hamas?
If the Palestinian had nuclear weapons would have surely used to erase Israel from the map.
This question asks for an opinion. At best it asks for an estimation. Using history as a reference, we know at least about a few things concerning atomic bombs:
-They do a lot of structural damage (Hiroshima and Nagasaki did, even though there are some nowadays which can damage organic tissue without destroying many buildings, but that's not history)
-They make the surroundings of the detonation point inhabitable for a while.
-They kill many civilians, and are therefore a huge hit to the PR of a country. (everybody is going to hate you)
Now, what we know about the geography of the middle east, international factions and terrorist groups might also be relevant:
-Countries in the middle east are not as far apart and isolated as the US and Japan are, and neither as big as Russia, so if one nukes the other, it might suffer some radiation too. Firing a nuke from Israel to Beirut is not dissimilar to firing a nuke from New Jersey to New York; and firing a nuke from Israel to the Gaza strip, is like firing a nuke from Bronx to Manhattan, and I don't see how that's good for either Bronx or Manhattan.
-Hamas is an international organization. To obliterate it, Israel would need to bomb countless cities and countries, and probably hasn't nearly enough nukes to do that, even if it tried. Maybe not even the US has.
-Terrorists in general make use of guerrilla tactics and operate in terrorist cells. They blend in perfectly with the civilian population (ideally), and no one actually knows who they are and where they are, which makes it impossible to strike against them in such crude fashion. Often, they operate in Israel itself, therefore Israel would not only have to kill civilians of other countries, but also of its own, on a much larger scale then they currently do.