“Truly, truly, I say to you, whoever believes in me will also do the works that I do; and greater works than these will he do, because I am going to the Father.”
People often argue away this one, but it seems clear to me, especially in the context of John 14 and the other Gospels, that Jesus is saying if you follow his teachings, then you will do greater things than Jesus.
Jesus often claimed in John’s Gospel that he did nothing by himself and that it was the Father in him that did everything. Jesus’s constant message to humanity was to turn away from the world and towards God, realise that God is Love, to love one another, to see the Kingdom of Heaven is within, and to surrender to God’s will. Not the worst teachings in the world, eh?