I know the Title must have made you shocked and wonder what the writer's saying. But the writer has a tangible reason for bringing up this title. Firstly, let's reminisce on what Robert thinks about himself and his monstrous goal hunger.
Robert Lewandowski said after he scored four in Bayern's Champions League thrashing: "I have to confess, I'm addicted to scoring."
With his goal-scoring ratio and form at the moment. Its clear to all, that the Polish is on an unplayable form. And he scores to destroy all teams Bayern faces at the moment.
Therefore, He can be referred to as dangerous, and hence a dangerous goal- addict.