Israel has been nice in the past. They've agreed to the 2 state solution several times. I'm not sure Arab terror organizations understand niceness as anything other than weakness.
Unlike Hamas leadership, I don't know what an acceptable ratio of death is. Bare numbers don't tell the whole story, when you are talking about Hamas going house to house killing peaceful families, raping women in front of their families, and killing children in front of their parents, and killing parents in front of their children...as the main goal of their attack, not as unintended byproduct of combat. Remember also that they are fighting genocide, something they suffered not too long ago. I'm glad I didn't have to make the decision to do what Israel did, but I also have a hard time condemning Israel for their reaction.