In Nagoya we have something called Taiwan Ramen. Despite it's name, it's not actually from Taiwan. While I'm sure it exists outside of Nagoya, I haven't really noticed it when traveling to other places in Japan. Something a bit more widespread would be Shinsen (how Japanese pronounce the Sichuan region of China) Ramen. For me personally, those are levels of spicy I like. I'm not really interested in torturing myself. I'd rather enjoy my food. I'm sure if you look hard enough though, there are probably places that have some really crazy spice levels for those more adventurous.
Although, I only have ramen like once every few months. Not really that big on it so that could be a contributing factor.