It is customary in Christian theological discourse and affiliated philosophy of religion literature to affirm that God is omnipotent. Often this attribute is joined to omniscience and moral perfection so as to form part of a triadic set of divine properties. What is the origin, if any, of the attribution of omnipotence to God in the ecumenical councils or other authorities binding for Christian churches?
The omnipotence of God is affirmed in the Creed set forth at the first Ecumenical Council in Nicea in 325: "We believe in one God, the Father Almighty [παντοκράτορ - pantokrator] ..."
As the Creed further affirmed that the Son and the Holy Spirit were of the same substance (ὁμοούσιον) as the Father, the Creed affirmed that all three persons of the share in the omnipotence of God.
Let me try to give a partial answer.
The biblical texts provide a variety of evidences, and are often tinted with poetical qualities that make them difficult to interpret.
Yes, but this is not always the case. It is also of course important to see who wrote a give scripture at what point.
As an orthodox Christian I therefore seek evidence that the ecumenical church councils or related theological authorities expressed that the mentioned ideas about God are part of Christian belief.
The first council(s) of the church is documented in the book of Acts. One of the attainers was St. John. From that fact we can defer, that whatever John believed was what that first council could at least agree to live with. There was no grounds for a division of the church at that point.
Now, putting those two together, we can for example see in John 1, 1 that he clearly states the omnipotence of God. So, from there we can infer that the consensus of the people who attained the first council did hold to an omnipotent God.