Of what I've watched, it's Dandadan and Frieren. If I have to pick a best one, it's the latter. Its fanservice is so subtle you won't notice if you are not aware.
I love how no one has said anything about Dandadan, because, of course it's Dandadan. If there's anything Dandadan is most definitely not, it's subtle.
Fun show, though, except when it chooses to traumatize the viewer for no apparent reason.