Should I leave my fiancée after a two-year engagement during which I grew to resent the frequent disagreements between us, and I fear I may be wronging her, especially as these thoughts coincided with hearing a Quranic verse about wrongdoers?

Engagement is not a binding commitment, and either party has the right to dissolve it at any time, especially if there is a reason to do so. Dissolving it without need is disliked. A promise of marriage does not necessitate fulfillment, and reciting Al-Fatiha is not considered a contract. Dissolving an engagement is not considered an injustice; if it is highly probable that the marriage will not last, then dissolving the engagement is easier than divorce after marriage.