To have Faith is to be sure of the things we hope for, to be certain of the things we cannot see. (Hebrews 11:1).
If I were to ask what is the opposite of Faith; some would say Doubt. Because Doubt makes you question what it is you believe, or have been taught to believe.
But what if I were to say that the opposite of Faith is Certainty.
Faith is believing in someone or something without any proof. In blind trust.
But what if you were certain that God exists? What if you were certain that Jesus is His only Son? What if you were certain that you are loved and cared for and that no matter what happens in life, you are certain that God is with you, and you are certain that it will all turn out right?
Faith is believing with your eyes closed perhaps.
The opposite of that is believing with eyes wide open and with Certainty.
"Have you believed because you have seen me? Blessed are those who have not seen and yet have come to believe." (John 20:19-31).