Final answer:
Nathanael called Jesus 'Rabbi', the Son of God, and the King of Israel after Jesus mentioned seeing him under the fig tree.
Step-by-step explanation:
When Jesus told Nathanael that He saw him under the fig tree, Nathanael responded with a declaration of faith, calling Jesus 'Rabbi' (which means teacher), the Son of God and the King of Israel. This encounter can be found in the biblical passage John 1:47-49. Nathanael's recognition of Jesus' divine insight, as well as his authority and identity, represents a significant moment of belief and recognition in the New Testament.