Oslo and Madrid come to mind. For the worst than london, The Rome underground is so sparse, it not really usefull. Paris is dense, chaotic and overcrowded.

Every single time I've been in Madrid the metro has been on strike. Every time. They run about 50-60% of services which means everything is slow and packed. I would actually say it's one of the worst in europe in my (I guess limited) experience due to that. I will have to try Oslo!