Question: who is the main villain in arrow season 4
[{'answer': 'Damien Darhk', 'provenance': [{'wikipedia_id': '39235131', 'title': 'List of Arrow characters', 'start_paragraph_id': 38, 'start_character': 62, 'end_paragraph_id': 38, 'end_character': 74, 'bleu_score': 1.0, 'section': 'Section::::Main characters.:Quentin Lance.\n'}]}]