ELDEN RING Boss Fight - Commander Niall

Why did this guy end up being the most difficult boss in the game thus far?

I had to get creative with my strategy and used 3 separate weapon configurations. I fought the dual sword knight with my Greatsword, two handed, then switch to one handing it with my large shield to fight the shield knight. The boss then had a bunch of moves which were VERY hard to punish, so I found that my best option was to switch to my small buckler shield and deal most of my damage by parrying his spear strikes.