• تَقْنَطُوا۟
• قَنَطُوا۟
• قَٰنِطِين
• قَنُوط
• يَقْنَطُ
• يَقْنَطُونَ

Appears 6 times in the Quran.

1. 15:55 قَالُوا۟ بَشَّرْنَٰكَ بِٱلْحَقِّ فَلَا تَكُن مِّنَ ٱلْقَٰنِطِينَ

   They said: We give you good news with truth, therefore be not of the despairing.
   

2. 15:56 قَالَ وَمَن يَقْنَطُ مِن رَّحْمَةِ رَبِّهِۦٓ إِلَّا ٱلضَّآلُّونَ

   He said: And who despairs of the mercy of his Lord but the erring ones?
   

3. 30:36 وَإِذَآ أَذَقْنَا ٱلنَّاسَ رَحْمَةً فَرِحُوا۟ بِهَا وَإِن تُصِبْهُمْ سَيِّئَةٌۢ بِمَا قَدَّمَتْ أَيْدِيهِمْ إِذَا هُمْ يَقْنَطُونَ

   And when We make people taste of mercy they rejoice in it, and if an evil befall them for what their hands have already wrought, lo! they are in despair.
   

4. 39:53 قُلْ يَٰعِبَادِىَ ٱلَّذِينَ أَسْرَفُوا۟ عَلَىٰٓ أَنفُسِهِمْ لَا تَقْنَطُوا۟ مِن رَّحْمَةِ ٱللَّهِ إِنَّ ٱللَّهَ يَغْفِرُ ٱلذُّنُوبَ جَمِيعًا إِنَّهُۥ هُوَ ٱلْغَفُورُ ٱلرَّحِيمُ

   Say: O my servants! who have acted extravagantly against their own souls, do not despair of the mercy of Allah; surely Allah forgives the faults altogether; surely He is the Forgiving the Merciful.
   

5. 41:49 لَّا يَسْـَٔمُ ٱلْإِنسَٰنُ مِن دُعَآءِ ٱلْخَيْرِ وَإِن مَّسَّهُ ٱلشَّرُّ فَيَـُٔوسٌ قَنُوطٌ

   Man is never tired of praying for good, and if evil touch him, then he is despairing, hopeless.
   

6. 42:28 وَهُوَ ٱلَّذِى يُنَزِّلُ ٱلْغَيْثَ مِنۢ بَعْدِ مَا قَنَطُوا۟ وَيَنشُرُ رَحْمَتَهُۥ وَهُوَ ٱلْوَلِىُّ ٱلْحَمِيدُ

   And He it is Who sends down the rain after they have despaired, and He unfolds His mercy; and He is the Guardian, the Praised One.