Dark

This easily could have been the best sci fi series ever made. Unfortunately the writers screwed up big time and decided to choose the easy way out. Just like in many other movies/shows, once the writers realise they have created an unsolvable problem, they suddenly introduce a parallel world to fix all the issues the writers couldn't solve themselves. As if that is not enough, they decide to do the same trick again through the concept of superposition, doubling the amount of worlds from 2 to 4.