How can one supplicate for a person so that Allah may grant him faith, guide him, and open his heart to Islam, despite his numerous sins and major transgressions?

A believer's faith in his Lord and his worship of Him are his capital with which he approaches Allah Almighty. So, whoever comes with faith will succeed and prosper, and whoever comes without faith will be fuel for Hell. Allah has filled His inscribed Book (the Qur’an) and His observable Book (the universe) with clear proofs and verses indicating His Lordship and Divinity, so learning them is among the important matters.