Translation
are you saying of the one whom the Father set apart as holy and sent into the world, ‘you blaspheme’ because I said ‘I am the son of the Mighty One’?
Paraphrase
are you saying I, the one whom the Father set apart as holy and sent into the world [to represent Him], am a blasphemer because I said ‘I am the son of the True Mighty One’?
A MIGHTY ONE IS PROVED MIGHTY BY HIS DEEDS
For an entity to be considered a “mighty one” he needed to have authority granted to him to rule or preside over other people, or he had to prove he possessed unusual powers to perform mighty deeds (miracles). The judges of Psalm 82 were called “mighty ones” because they had been granted authority to make decisions based on the Law given by God through Moses. The fact that Jesus was not born with authority, and neither was he granted authority by any human institution, made His miracles stand as proofs that He had power that was beyond human means.
This whole passages is focused on Jesus’ deeds. Jesus was forcing the religious leaders to confront the question – Did the miracles of Jesus proof He was one with God and the Son of God, or not?