Children are the prized poker chips in war today and not just adult civilians. Hamas kidnapped kids for later trades. Putin has taken upwards to 100K Ukrainian kids to be raised in Russia. Trump separated kids from families without records for reuniting families. Sure these examples are a crime but no one is going to jail. Maybe someday Putin will be imprisoned. Maybe Steve Bannon will end up behind bars. Trump?
The odds are slim.
War is a willingness to forgo laws and civilized behavior up to and including nuclear and bioweapons. Proportionality is not a deterrent.
The deterrent is whether a country decides if it can withstand the blowback from global retribution.
Proportionality is heartwarming like a cup of hot cocoa but it will not curb the crime of war. The easiest way to sidestep proportionality historically has been to claim an attack upon a ship or ships. Even a bald faced lie is all it takes. The Hamas attack was not a lie.