The word(s) "stern" appears 15 time(s) in 14 verse(s) in Quran in Muhammad Pickthal translation.

(1) It was by the mercy of Allah that thou wast lenient with them (O Muhammad), for if thou hadst been stern and fierce of heart they would have dispersed from round about thee. So pardon them and ask forgiveness for them and consult with them upon the conduct of affairs. And when thou art resolved, then put thy trust in Allah. Lo! Allah loveth those who put their trust (in Him).

(2) O ye who believe! Whoso of you becometh a renegade from his religion, (know that in his stead) Allah will bring a people whom He loveth and who love Him, humble toward believers, stern toward disbelievers, striving in the way of Allah, and fearing not the blame of any blamer. Such is the grace of Allah which He giveth unto whom He will. Allah is All-Embracing, All-Knowing.

(3) And We caused the folk who were despised to inherit the eastern parts of the land and the western parts thereof which We had blessed. And the fair word of thy Lord was fulfilled for the Children of Israel because of their endurance; and We annihilated (all) that Pharaoh and his folk had done and that they had contrived.

(4) (But hath made it) straight, to give warning of stern punishment from Him, and to bring unto the believers who do good works the news that theirs will be a fair reward,

(5) (Pharaoh) said: Ye put faith in him before I give you leave. Lo! he is your chief who taught you magic. Now surely I shall cut off your hands and your feet alternately, and I shall crucify you on the trunks of palm trees, and ye shall know for certain which of us hath sterner and more lasting punishment.

(6) Thus do We reward him who is prodigal and believeth not the revelations of his Lord; and verily the doom of the Hereafter will be sterner and more lasting.

(7) And thou (Muhammad) wast not on the western side (of the Mount) when We expounded unto Moses the commandment, and thou wast not among those present;

(8) The Forgiver of sin, the Accepter of repentance, the stern in punishment, the Bountiful. There is no Allah save Him. Unto Him is the journeying.

(9) That is because they were opposed to Allah and His messenger; and whoso is opposed to Allah, (for him) verily Allah is stern in reprisal.

(10) That which Allah giveth as spoil unto His messenger from the people of the townships, it is for Allah and His messenger and for the near of kin and the orphans and the needy and the wayfarer, that it become not a commodity between the rich among you. And whatsoever the messenger giveth you, take it. And whatsoever he forbiddeth, abstain (from it). And keep your duty to Allah. Lo! Allah is stern in reprisal.