Regardless of how Robert Kubica fares on his Formula 1 return with Williams in 2019, he will likely always be regarded as a world champion who should have been but never was.
With most drivers, you have to caveat such a statement. In particular, there's the question of how they would stand up mentally to the intensity of a season-long fight for supremacy, for many great 'talents' have crumbled under such pressure. It takes a special mindset to thrive consistently in elite sport, and that can only be tested in battle.
But in the case of Kubica, we can now say definitively that he would have been world champion. That's assuming he would have made it into a title-worthy car, which is a likely given he was destined to move to Ferrari in 2012.