Pope Benedict XVI said,
The kingship of Christ remained completely hidden until he was 30 years old, years spent in an ordinary life in Nazareth. Then, during his public life, Jesus inaugurated the new Kingdom which "does not belong to this world" (Jn 18: 36), and finally, with his death and Resurrection, he fully established it.
The text the Pope references continues with John 18:37,
“Pilate said to him, ‘So you are a king?’ Jesus answered, ‘You say that I am a king. For this I was born, and for this I have come into the world, to bear witness to the truth. Every one who is of the truth hears my voice.’”
Matthew 28:18 likewise says, “And Jesus came and said to them, ‘All authority in heaven and on earth has been given to me.’”
There are other references to Jesus’ kingly reign, such 1 Corinthians 15:25-28 and Philippians 2:10-11: “… at the name of Jesus every knee should bow, in heaven and on earth and under the earth, and every tongue confess that Jesus Christ is Lord, to the glory of God the Father.”
Doesn’t the title INRI on crucifixes point to Christ’s Kingship?
Yes, these are the initials for the Latin Iesus Nazarenus Rex Iudaeorum, which means “Jesus of Nazareth, King of the Jews.” Pilate ordered that a sign with these ironic words be placed on Jesus’ cross above His head. Even though this was done to justify the Crucifixion, and not because Pilate believed it to be true, it was still fitting that the Cross in some way acknowledged Jesus’ Kingship.