In Phantom of the Opera who is the Flat Character?

In "The Phantom of the Opera," the flat character is often considered to be Raoul, the Vicomte de Chagny. He serves primarily as a love interest for Christine Daaé and represents the archetype of the romantic hero. While he is brave and noble, his character lacks the depth and complexity seen in other characters like the Phantom or Christine, making him more one-dimensional throughout the story.