What is the grammatical and semantic role of tawwāban?

Supplementary Practice 22: Comparative Rhetorical Study of Sūrat al-Kāfirūn and al-Naṣr

• A negative particle denying repentance
• A second object of raʾayta describing people
• Accusative predicate of kāna; its intensive form conveys abundant acceptance of repentance
• An imperative directly commanding the audience to repent