Eric Birling
Eric's the most troubled character in the play, struggling with alcohol, guilt, and his own moral failings. He's described as "not quite at ease, half shy, half assertive", which perfectly captures his awkward personality and internal conflicts.
His treatment of Eva Smith is the most disturbing in the play. Eric forced himself into her lodgings when drunk, made her pregnant, then stole money from his father's business to support her. When he says "I was in a state where a chap easily turns nasty", he's essentially admitting to rape whilst trying to excuse his behaviour.
Despite his terrible actions, Eric does show moral growth by the end. He accepts full responsibility for his part in Eva's death and stands up to his parents, calling them out for their lack of compassion. Like Sheila, he represents hope that the younger generation can change.
Important point: Eric's character shows how privilege and alcohol can lead to the abuse of power, but also demonstrates that genuine remorse can lead to positive change.