The US defined combatant in their latest wars as any male killed over the age of 14, so the ratio is a bit up to how people choose to define combatant vs civilian.

The wikipedia article should be read as a starting point in understanding how extremely unreliable those numbers are, and how much it depend on how people define combatant and civilian.

The article also gives examples of many major wars, with the majority of examples have numbers of civilians killed usually greater than combatants.

So, as horrific as this war has been, I don't think the claim that this is "one of the the deadliest wars for civilians in general" holds up.

Israel estimated 12,000 Hamas at a time when Hamas figures claimed 26,000 dead. That's pretty close to 1:1.

Part of the trouble is Israel can't prove the 12,000, and no one actually believes the Hamas figures are legitimate. But there are not better figures available for either number. So 1:1 for Gaza is the best we can estimate.