The worst seat on a plane, IMO, is a bulkhead seat. Those are the ones that have a white wall in front of them. There’s no place for your feet. There’s no place for your eyes. It’s confining. Planes are already confining enough without that.
I’ve actually given up a First Class bulkhead seat for a coach seat! Now granted, it was on a CRJ-700 where the First Class is fairly limited (can’t even stand up in the bathroom). And I was moving to an exit row. And my only motivation was to kick my feet out and sleep. But still, bulkheads suck!