The word(s) "painful" appears 75 time(s) in 75 verse(s) in Quran in Mohsin Khan translation.

(21) O you who believe! Verily, there are many of the (Jewish) rabbis and the (Christian) monks who devour the wealth of mankind in falsehood, and hinder (them) from the Way of Allah (i.e. Allah's religion of Islamic Monotheism). And those who hoard up gold and silver [Al-Kanz: the money, the Zakat of which has not been paid] and spend them not in the Way of Allah, announce unto them a painful torment.

(22) If you march not forth, He will punish you with a painful torment and will replace you by another people; and you cannot harm Him at all, and Allah is Able to do all things.

(23) And among them are men who annoy the Prophet (Muhammad صلى الله عليه وسلم) and say: "He is (lending his) ear (to every news)." Say: "He listens to what is best for you; he believes in Allah, has faith in the believers, and is a mercy to those of you who believe." But those who annoy Allah's Messenger (Muhammad صلى الله عليه وسلم) will have a painful torment. [See V.33:57]

(24) They swear by Allah that they said nothing (bad), but really they said the word of disbelief, and they disbelieved after accepting Islam, and they resolved that (plot to murder Prophet Muhammad صلى الله عليه وسلم) which they were unable to carry out, and they could not find any cause to do so except that Allah and His Messenger had enriched them of His Bounty. If then they repent, it will be better for them, but if they turn away, Allah will punish them with a painful torment in this worldly life and in the Hereafter. And there is none for them on earth as a Wali (supporter, protector) or a helper.

(25) Those who defame such of the believers who give charity (in Allah's Cause) voluntarily, and such who could not find to give charity (in Allah's Cause) except what is available to them - so they mock at them (believers); Allah will throw back their mockery on them, and they shall have a painful torment.

(26) And those who made excuses from the bedouins came (to you, O Prophet صلى الله عليه وسلم) asking your permission to exempt them (from the battle), and those who had lied to Allah and His Messenger sat at home (without asking the permission for it); a painful torment will seize those of them who disbelieve.

(27) To Him is the return of all of you. The Promise of Allah is true. It is He Who begins the creation and then will repeat it, that He may reward with justice those who believed (in the Oneness of Allah - Islamic Monotheism) and did deeds of righteousness. But those who disbelieved will have a drink of boiling fluids and painful torment because they used to disbelieve.

(28) And Musa (Moses) said: "Our Lord! You have indeed bestowed on Fir'aun (Pharaoh) and his chiefs splendour and wealth in the life of this world, our Lord! that they may lead men astray from Your Path. Our Lord! Destroy their wealth, and harden their hearts, so that they will not believe until they see the painful torment."

(29) Even if every sign should come to them, until they see the painful torment.

(30) "That you worship none but Allah; surely, I fear for you the torment of a painful Day."