Genesis 1:1 
In the beginning, God created the heavens and the earth.
The very first verse in the bible teaches that God created the whole universe.

John 1:1 
In the beginning was the Word, and the Word was with God, and the Word was God.

The term ‘Word’ is a poor English translation of the Greek word logos, which is better understood as reason or logic, I recommend Gordon H Clark book “The Johannine Logos” to learn more about the logos. We learn as we continue reading chapter 1 of John that Jesus is the logos. We can deduce from this verse that Jesus in the beginning before he became man created the universe. This is also supported by other texts.

Colossians 1:16
For by him all things were created, in heaven and on earth, visible and invisible, whether thrones or dominions or rulers or authorities—all things were created through him and for him.

There is nothing that exists in the universe that was not made through Jesus, anything that has a beginning has been created. God has no beginning and therefore was not created, there is only one God that has been there from the beginning, all other gods and lords have been created and serve the true God. If there is another world that exist other than earth, we can know for certain that it was through Jesus that it was created. There is no other God or creator, if other worlds existed then it still remains true that there is only one God who rules over all.

1 Corinthians 8:
⁵ For although there may be so-called gods in heaven or on earth—as indeed there are many “gods” and many “lords”— ⁶ yet for us there is one God, the Father, from whom are all things and for whom we exist, and one Lord, Jesus Christ, through whom are all things and through whom we exist.

Isaiah 43:10,11
¹⁰“You are my witnesses,” declares the Lord, “and my servant whom I have chosen, that you may know and believe me and understand that I am he. Before me no god was formed, nor shall there be any after me. ¹¹, I am the Lord, and besides me there is no savior.

There is no other Saviour, Christ has died only for his people, he has not died for angels or other beings.

Hebrews 2:16
For surely it is not the angels He helps, but the descendants of Abraham. 

In order for us to be saved Christ had to become like us in everyway but without sin he became fully human while he was also fully God.

Hebrews 2:14,17
¹⁴Now since the children have flesh and blood, He too shared in their humanity, so that by His death He might destroy him who holds the power of death, that is, the devil, 15and free those who all their lives were held in slavery by their fear of death.
¹⁷Therefore he had to be made like his brothers in every respect, so that he might become a merciful and faithful high priest in the service of God, to make propitiation for the sins of the people.

 Jesus now remains fully human and fully God forever sitting at his Fathers right hand.

Hebrews 1:3
He is the radiance of the glory of God and the exact imprint of his nature, and he upholds the universe by the word of his power. After making purification for sins, he sat down at the right hand of the Majesty on high,

If there existed sinners on other worlds, Jesus intention was not to bring them a saviour, for to be a saviour he had to become like them in every way except sin to atone for their sin, since we have learnt he has become fully man and fully God forever his intention was only to save people from their sins, he cannot change his being into something else, for this will distort who he is and contradict what the scriptures speak of him. This is why the angels who have fallen won’t receive help from the Lord, he did not intend to become an angel and die for them, those that are fallen will remain fallen forever and God has reserved the lake of fire for them after the great white throne of judgement.

Matthew 25:41
41 “Then he will say to those on his left, ‘Depart from me, you cursed, into the eternal fire prepared for the devil and his angels.

Jude 1:25 
To the only God, our Savior, through Jesus Christ our Lord, be glory, majesty, dominion, and authority, before all time and now and forever. Amen.