Pilate

Pilate, being a Roman, believed in the old Roman Gods.

He would also have heard all the stories about demi-Gods, how the Gods would impregnate mortal women and have half-mortal children with them. It would have been conceievable to a Roman mind that Mary was impregnated by Jupiter, King of the Gods. If the stories about Jesus and his miracles were true, this would make the stories all the more believable.

So if Pilate killed JC he would have been killing the son of Jupiter, Not good. Hence washing his hands of the matter and handing JC back to the Jews to deal with in their own way.

Pilate feared the wrath of Jupiter.