Psalms 86:10

For thou art great, and doest wondrous things: thou art God alone.

Psalm 86 comes from the sons of Korah, inspired singers of God in the priestly tribe.
God is great and does wondrous things, and he is God alone, with no other god like him.

His uniqueness as God alone is seen in mercy toward sinful and erring people, in readiness to forgive, and in abundant mercy to all who call upon him.
All the nations he has made will come to worship before him and glorify his name.

The title God alone is a title of supremacy belonging to the Father.
This title of supremacy is not applied to the Son.