God Is Just
Although suffering is used by God to deepen our love and trust, pain and injury are not good; and those who cause suffering will be dealt with by God. In the Old Testament, even though the Lord used the Assyrian and Babylonian exiles to discipline His people, those nations were eventually punished for their arrogance in capturing God's people (Isaiah 10:5-12; 13:17-22). Paul commends the Thessalonians for their love, faith and patient endurance of persecution (2 Thessalonians 1:4), but also wants to reassure them that the Lord is fully in command of the situation: He will deal with the trouble-makers.
When people suffer because others sin against them, some like to think that they will have the satisfaction of seeing justice done. But God's scale of values and time is different. He certainly does bring relief and comfort the broken hearted (Isaiah 61:1). Although all sin is ultimately against God (Psalm 51:4), He does not treat us as our sins deserve (Psalm 103:10). He wants to forgive the penitent, and gives time for sinners to repent and seek His mercy (2 Peter 3:9). It is all possible because God the Father laid on God the Son the sins of all of us (Isaiah 53:6). And whatever discipline He may bring is only so that the person may be fully restored (Hebrews 12:11).
But for those who spurn His love, despise His mercy and frustrate His grace there is no forgiveness: only eternal judgement (Hebrews 10:26-27). That is not immediate, because God waits patiently for repentance; but if there is no repentance, His justice is eternal. This will happen on the day the Lord Jesus Christ returns – a day of salvation for those who trust in Him, and of deep remorse for those who have resisted His love (Zephaniah 1:14-18; Revelation 1:7).
God is just. He saves those who repent, because the punishment has already been taken by Jesus (1 John 1:9). He will comfort believers in distress and give them a heart of love for those who sin against them. He waits to give sinners the opportunity to respond to the gospel, that they might be saved (1 Corinthians 6:9-11). But when Jesus comes again He will punish all who refuse to obey the gospel. That is why gospel proclamation is urgent. Saving faith comes only by believing the gospel of Jesus (Romans 10:17). Even persecutors can be saved if they repent and receive Christ - Paul knew that personally because, previously, he had also been a persecutor (Galatians 1:13-17) and God had mercy on him (1 Timothy 1:13). So, if you are being tormented by persecutors, pray for them (Matthew 5:44) and trust the Lord to strengthen you. Always speak the truth about Jesus and be confident that He is in command, now and for eternity.