It is No Man's Sky. Although a critical failure, No Man's Sky support over 18 quintillion planets. It was released in 2016 and is an integrated multiplayer and single player experience. Its extensive marketing strategy failed it because the game world is so large you almost have nohing to do in it.
Even in its multiplayer, you have a very very rare chance to run into another player just due to the sheer size of its rendered world. Its creators say that it would take an actual billion years just to explore its world to an entirety. It achieves this sheer size due to the fact that the game renders the universe as you play and nothing is pre-rendered.