Evidence from the Bible that God is not cruel, evil, or psychopathic in the way He judges people is the fact that the imperfect faith of even a single man who yearns to please God can reduce or stop His righteous judgments altogether. Consider:

• God planned to wipe out all mankind with the Flood, but because Noah was faithful (Genesis 6:8), all that exists today was allowed to come from him.
• All the blessings that came to persistently faithless Israel were because of the imperfect attempts of Abraham, Isaac, and Jacob to walk in faithfulness (see, for example, 2 Kings 13:23).
• Sodom was so wicked that every single man in the town wanted to gang rape the angels disguised as innocent strangers (Genesis 19:4-5). Usually people focus on the homosexual aspect of this story, but I think the more salient concern is the violent gang-banging, especially because a similar story in Judges 19 (which only involved some men in Gibeah and not the entire town) implies the men of Sodom probably would have raped their victims to death. Nonetheless, had the angels found just ten righteous men in Sodom, God would have spared the entire city (Genesis 18:32).
• God spared the Davidic kings and the nation of Judah much longer than they deserved, all because David tried to please Him many years before (1 Kings 15:4-5).
• Finally, of course, Jesus’ 37-year life of perfect service and sacrifice allows any man or woman for the rest of eternity, no matter how evil he or she may be, to completely escape the punishment for his or her sins through faith in Christ.

This patient, long-suffering, and generous aspect of God’s nature is reflected in the Ten Commandments:

For I, the Lord your God, am a jealous God, visiting the iniquity of the fathers upon the children to the third and fourth generations of those who hate Me, but showing mercy to thousands, to those who love Me and keep My commandments. (Exodus 20:5-6; Deuteronomy 5:9-10)

While God’s wrath burns out and is replaced with a clean slate, His mercy endures for a near-infinite length of time. After all, a generation in the Bible is 40 years, so “a thousand generations” would be 40,000 years, almost seven times the entirety of human history up to this point (according to the Bible timeline). However, God speaks here of multiple “thousands” of generations, so that’s 80,000 to 120,000 years minimum. And, of course, if at any point during that 120,000 years one of those descendants were to pursue righteousness with a whole heart, the clock would reset on his or her entire line of descendants.

The point is, God is speaking of His mercy being virtually inexhaustible. Imagine yourself being treated with patience and understanding solely because your great-great-great-great-great grandfather loved and served God. Such is the kindness and long-suffering of the God of the Bible.