The word(s) "could" appears 96 time(s) in 90 verse(s) in Quran in Mohsin Khan translation.

(31) "And I have followed the religion of my fathers, - Ibrahim (Abraham), Ishaq (Isaac) and Ya'qub (Jacob) [عليهم السلام], and never could we attribute any partners whatsoever to Allah. This is from the Grace of Allah to us and to mankind, but most men thank not (i.e. they neither believe in Allah, nor worship Him).

(32) So he [Yusuf (Joseph)] began (the search) in their bags before the bag of his brother. Then he brought it out of his brother's bag. Thus did We plan for Yusuf (Joseph). He could not take his brother by the law of the king (as a slave), except that Allah willed it. (So Allah made the brothers to bind themselves with their way of "punishment, i.e. enslaving of a thief.") We raise to degrees whom We will, but over all those endowed with knowledge is the All-Knowing (Allah).

(33) "Return to your father and say, 'O our father! Verily, your son (Benjamin) has stolen, and we testify not except according to what we know, and we could not know the Unseen!

(34) And if there had been a Qur'an with which mountains could be moved (from their places), or the earth could be cloven asunder, or the dead could be made to speak (it would not have been other than this Qur'an). But the decision of all things is certainly with Allah. Have not then those who believed yet known that had Allah willed, He could have guided all mankind? And a disaster will not cease to strike those who disbelieved because of their (evil) deeds or it (i.e. the disaster) settles close to their homes, until the Promise of Allah comes to pass. Certainly, Allah breaks not His Promise.

(35) And they carry your loads to a land that you could not reach except with great trouble to yourselves. Truly, your Lord is full of Kindness, Most Merciful.

(36) And if you would count the favours of Allah, never could you be able to count them. Truly! Allah is Oft-Forgiving, Most Merciful.

(37) And had Allah willed, He could have made you (all) one nation, but He sends astray whom He wills and guides whom He wills. But you shall certainly be called to account for what you used to do.

(38) And if We willed, We could surely take away that which We have revealed to you (i.e. this Qur'an). Then you would find no protector for you against Us in that respect.

(39) Say: "If the mankind and the jinn were together to produce the like of this Qur'an, they could not produce the like thereof, even if they helped one another."

(40) So his fruits were encircled (with ruin). And he remained clapping his hands (with sorrow) over what he had spent upon it, while it was all destroyed on its trellises, and he could only say: "Would that I had ascribed no partners to my Lord!" [Tafsir Ibn Kathir]