I’m not referring to everything as a war crime. Here’s a list of war crimes as defined by the UN: https://www.un.org/en/genocideprevention/war-crimes.shtml

Hamas committed war crimes by killing civilians, taking hostages, and using human shields. I’ve seen rumors they used sexual violence as a weapon too.

Israel’s use of collective punishment, destroying civilian infrastructure, and cutting off food and water are also war crimes. Israel is probably violating the proportionality standard. (It definitely has in the past.)