The worst among creatures in Allah's Sight are those who are bent on denying the Truth. They show ingratitude by not using their God-given faculties and thus fail to believe
The worst of living creatures in the sight of Allah are those who deny the knowledge of the reality! They will not believe!
Sayyed Abbas Sadr-Ameli
Verily the worst of animals in Allah�s sight are those who disbelieve, so they will not have faith
Al-muntakhab fi tafsir al-Qur'an al-Karim
Indeed, the worst creatures in Allah's sight are those whose hearts' ears are closed and whose minds' eyes are blind, who counsel deaf to divine discourse and disavow Allah