I have a giant noggin and wear all my headphone bands on the max setting, for reference.
I've found all Sennheiser headphones to be very comfortable. I wear a pair of HD800s all day long, every day when working.
I had HE400i for a while but I did not find them super comfortable, but it was tolerable for all day wear. I ordered an audeze suspension kit online to try and fix it, but I ended up just returning them before the return window ended.
Focal Clears I found very uncomfortable. They are heavy and have minimal padding on the headband, so I couldn't wear them for more than a couple hours before developing a sore pain point on the top of my head. I'm guessing the headband could be modded for more comfort but it's still heavy. Based on this experience I've ruled out any headphones >400g (sorry Audeze/Focal).
I have a pair of AKG K712 Pro for gaming/backup and they are super comfortable, on par with Sennheiser.
Also have some Bose QC35 II for travel and working at coffee shops. These are my only closed pair. They are supremely comfortable, like wearing pillows. However they do get very sweaty so I can't wear them when it's too warm. I guess this is the con of closed headphones.
I can't stand IEMs. I have narrow ear canals and I find them all very uncomfortable. I think with IEMs you either love them or hate them. I have a pair of airpods which are comfy though (but terrible sound).
I think the key for comfort is lightweight headphones mostly made of plastic.