The first hard fork took place at block #478559 on 1 August 2017, which transformed into a Bitcoin Cash (BCH), that offers larger blocks (up to 8 megabytes at the start).
To be candid, the August 2017 Bitcoin fork was the one that held the highest uncertainty and apprehension in the crypto community. I was a noob then but I felt the tension in the market. It was as thick as a Russian snow. The market literarily paused and as soon as the fork successfully birthed BCH, everything went on a high drive and Bitcoin went on to record its ATH. Thank you OP for drawing our attention to this. Sincerely, I didn't know we had so many forks as listed.
and some protocol experiments / variations - incl segwit (just since that Aug 2017)