1. God allows evil to a great extent for the complete and ultimate destruction of evil and sin through Jesus Christ (Col 2:13–15; Heb 2:14–18; 1 John 3:8).
2. God allows evil so that people who sin can continue living by God’s mercy to have opportunity to repent, because God loves all and wants everyone to repent and be saved (1 Tim 2:4; 2 Pet 3:9).
3. God gives free will and the ability for humanity to choose to flee sin and pursue holiness (Rom 6:15–19).
4. God allows evil and that allows the greatest acts of good — repentance, mercy, compassion, forgiveness, comfort, and relief — that cannot exist otherwise (Luke 5:32; 6:20–49).
5. God allows evil with great suffering for those who suffer greatly can experience the grace of God that gives peace in Jesus Christ (Rom 8:16; Phil 1:27–30; Jas 1:2–4; cf. 1 Pet 3:14; 4:1, 12; 5:10).
6. God allows evil and suffering as God’s grace strengthens a person’s character through suffering that cannot exist without suffering (Rom 5:3–5; 8:16, 28; 2 Cor 12:7–10).
7. God resolves suffering justly and overcomes death in Jesus’s resurrection. God will give eternal afterlife by restoring creation from corruption and decay. This is the redemption of the faithful by bodily resurrecting them from the dead (Rom 8:18–25; 2 Cor 4:17).
[If you know of another reason from Scripture, please comment below so that I can consider adding it to the list. Thank you.]