Yep, in Acts it was Peter, but he wasn't just expressing his opinion - he was an eyewitness. Jesus was anointed at his baptism. Jesus is God's Messiah, the Lord's Christ.
God did not come down to earth - God or gods coming down to earth is a pagan belief. Jesus did not have "innate powers and authority" - scripture says that God did the mighty works and wonders and signs through him.
In Jewish culture (OT), it takes two or three witnesses to confirm a fact. In John 5 Jesus says: Truly, truly, I say to you the Son can do nothing of his own accord but only what he sees the Father doing. For whatever the Father does, that the Son does likewise . . . I can do nothing on my own. As I hear I judge, and my judgment is just, because I seek not my own will but the will of him who sent me. If I alone bear witness about myself, my testimony is not true. There is another who bears witness about me, and I know that the testimony that he bears about me is true. You sent to John, and he has borne witness to the truth. Not that the testimony that I receive is from man, but I say these things so that you may be saved . . . But the testimony that I have is greater than that of John. For the works that the Father has given me to accomplish, the very works that I am doing, bear witness about me that the Father has sent me.
Who is the other witness Jesus is talking about? Now if Jesus is God and God is the other witness who is not a man and is greater than John - then we have a conundrum - two Gods.