السلام عليكم
It's incredible how true this is. There are certainly people out there, that no matter what, would reject any sign that God shows them.
I remember asking an Atheist; "If you saw Jesus(عليه الصلاة والسلام) raise someone from the dead in front of you, would you become a believer?" His reply was, "No, I'd just think it was some kind of magic trick or rational explanation for it".
Subhanallah, the following verse immediately came to mind.
وَلَوْ فَتَحْنَا عَلَيْهِم بَابًا مِّنَ السَّمَاءِ فَظَلُّوا فِيهِ يَعْرُجُونَ لَقَالُوا إِنَّمَا سُكِّرَتْ أَبْصَارُنَا بَلْ نَحْنُ قَوْمٌ مَّسْحُورُونَ
And [even] if We opened to them a gate from the heaven and they continued therein to ascend, They would say, "Our eyes have only been dazzled. Rather, we are a people affected by magic." [Qur'an 15:14-15]