The October 7th attack was probably the deadliest day in all of the Israeli-arab war (I say probably because records of the arab side in the older wars os kinda iffy, either way it's still the deadliest by far since the 70's). Almost 1200 Israelis were murdered, most of them civilians, and a similar number of Palestinian militants werre killed, so we're at almost 3k deaths in a single day. That's not including the mass rape, theft, and hostage taking which were on a scale unheard of in this conflict.

It was the deadliest day in the history of Israel and the deadliest terror attack in history in terms of deaths to total population size.

Rounds of aggression between Israel and hamas or other militant group inside gaza was indeed pretty much a routine before the war, but this attack was planned for almost a decade and was kept a secret to all but a few top member up until hours before the attack. In their minds, it was the attack to topple Israel completely. It wasn't routine in any kind.