This Psalm calls down curses upon those who have opposed the Psalmist.
See verses 1-8, 26.

Sometimes we hear that these prayers were acceptable in the Old Testament but they are not acceptable today.
In the OT God's people were encouraged to love their enemies- Exodus 23:4-5; Prov. 25:21-22.
In the OT God's people were forbidden from taking personal vengeance- Proverbs 20:22; 24:29.
In the NT we find God's people calling down curses upon the wicked- I Cor. 16:22; Galatians 1:8-9; 5:12; Rev. 6:9-10.
In the NT we find rejoicing at the fall of evil and wicked people- Rev. 18:20; 19:1-6

This is not an effort to eliminate Matthew 5:43-48; Luke 6:27-36; Luke 23:34, or Acts 7:59-60 from the Bible. It is an effort to say that prayers of judgement also have their place.

These prayers show us
That evil is real- Isaiah 5:20- and that we must be outraged by evil- Psalm 119:104, 128, 163.
These prayers do not encourage personal vengeance but they leave things in the hand of God- Psalm 35:13-14; II Timothy 4:14.
The prayers are motivated by a desire that God be glorified- Psalm 58:11; 59:13.