I think you need to get a reality check about war.
Anyone who tells you they can wage a war without civilian casualties is either naive, stupid or a liar.
The minute any regime/country/aggressor puts munitions, staff, leaders, operatives or any part of their War Machine covertly or visibly under/beside/above civilians, then that area becomes a legitimate military target.
And Israel didn't just kill 1 Hamas Commander, they destroyed a large section of the tunnel network (that's why the crater was so big, the whole lot just collapsed in on itself) and probably other parts of Hamas' infrastructure that they aren't revealing.
Do you really believe Israel chooses to drop bombs costing £1,00,000s just because they like seeing a firework display? These guided munitions are programmed to hit a target at particular co-ordinates based on intelligence.
It's easy to be an armchair critic.