There's a lot of great specific examples in this thread but I think it all boils down to this one quality; being able to put your own ego aside.

I think what lets a developer graduate from one level to the next is realizing that your own knowledge, vision, etc. is limited and not always the right way to go. Being able to put your own desires aside and execute someone else's vision while still providing the benefit of your experience and knowledge when appropriate.

Despite being a senior dev for a while now it's something I sometimes still struggle with finding the balance on.