Being militarily more powerful does not imply that they don’t want to avoid civilian casualties. Fighting an enemy who primarily employ terrorist tactics causes a large amount of civilian casualties, and Gaza being one of the most densely populated areas in the world makes it even worse.
If we consider some sort of an upper limit how many civilians you theoretically could kill, there’s nazis. They killed 1,5 million jews in 100 days. And that’s only jews. Now, you don’t have to be redoing the holocaust in order to qualify for an atrocity of course, but Israel is definetely not trying to kill as many civilians as they can. This would look very different if they were.