Job expresses deep pain over a sudden and unexplained shift in how he is treated, contrasting the natural mercy of the divine with the harsh suffering he now endures. He struggles to understand how a relationship once defined by compassion could transform so drastically.
The primary approach among commentators is that Job is bewildered by what appears to be a complete reversal of God's character. God is naturally merciful, and His past relationship with Job was filled with compassion. Now, however, it seems as though God has become cruel toward him [רמב״ן, מצודת דוד]. Job feels that God is actively using His immense power to show hatred and hold a deep grudge against him [מצודת דוד, רלב״ג].
A completely different perspective suggests that the cruelty Job experiences does not actually describe God at all. Instead, Job is crying out because God has turned away and handed him over to the control of a cruel entity, Satan. From this viewpoint, Job argues that even if he had committed a sin that required cleansing, he should have been judged directly by God. Direct judgment from God would be rooted in mercy, rather than the physical devastation caused by being surrendered to Satan [אלשיך].
Building on this idea, Job declares that if God had chosen to punish him directly, the outcome would have been different. Even if God had used His great power to express anger and hostility, His inherent mercy and His ability to tell the righteous from the wicked would eventually lead Him to examine Job's true actions and calm His wrath. The endless nature of Job's current torment stems entirely from being abandoned to the hands of a cruel force [אלשיך].