For a Mumin (believer) faith cannot be constituted based only on khaauf or fear of Allah's punishments. In Islam, faith or imaan is like a scale which can only be balanced if hope of Allah's mercy and fear of His punishments weigh equally on both sides. If one of them is heavier than the other it will cause one’s faith to become imbalanced. People have a natural tendency to cling on to Allah's mercy without making efforts to do good or they might fear Him to the point where they’ll have no love and respect for Him. Both are contrary to the purpose of Quran's message for humanity. Hence one finds statements mentioned throughout the Quran that give warning of His punishment while simultaneously giving good news of His mercy and grace in the hereafter for the sake of creating the balance of imaan (faith) in our hearts. Such as Allah ﷻ says: (Al Quran 42:21–22) "The evildoers will have a grievous punishment. you will see them fearful because of what they have done: punishment is bound to fall on them- but those who believe and do good deeds will be in the flowering meadows of the Gardens. They will have whatever they wish from their Lord: this is the great bounty."
One can find in Quran many statements which make reference to promises of His mercy and rewards for the good alongside threats of punishment and hell fire for the evil. Allah ﷻ refers to them in the Quran as mathani which means "paired statements" or "repeating statements": (Al Quran 39:23) "God has sent down the most beautiful of all teachings: a Scripture that is consistent and which repeats its contents in manifold forms (mathani); that causes the skins of those in awe of their Lord to shiver. Then their skins and their hearts soften at the mention of God: such is God’s guidance. He guides with it whoever He will; no one can guide those God leaves to stray." In Al Quran 39:23 Allah ﷻ very clearly informs us that such statements are there to generate fear but at the same time promises of hope for His mercy and His remembrance (zikr) are sources of calmness and provide peace to our hearts. Therefore, when addressing a reader, the Quran does not single out a threat for sinners without having mentioned mercy for the good unless the verse is strictly addressing warning only for the evildoers and disbelievers.
However an important thing to mention here is that besides the fact that Allah ﷻ mentions punishment and mercy throughout the Quran, He does hint in a few places that His mercy is greater than His punishment and this is a good news for disbelievers & believers: (Al Quran 7:156) "…..[God] answered: "With My chastisement do I afflict whom I will - but My grace overspreads everything: and so I shall confer it on those who are conscious of Me and spend in charity, and who believe in Our messages."