Human Ingratitude (Kufr)

وَهُوَ ٱلَّذِىٓ أَحْيَاكُمْ ثُمَّ يُمِيتُكُمْ ثُمَّ يُحْيِيكُمْ ۗ إِنَّ ٱلْإِنسَـٰنَ لَكَفُورٌ

And He is the one who gave you life; then He causes you to die and then will [again] give you life. Indeed, mankind is ungrateful.