And I will establish my covenant with you; neither shall all flesh be cut off any more by the waters of a flood; neither shall there any more be a flood to destroy the earth.
The second coming of Jesus is an unconditional promise. However, the timing is conditional.
John 14:2-3
In my Father's house are many mansions: if it were not so, I would have told you. I go to prepare a place for you. [3] And if I go and prepare a place for you, I will come again, and receive you unto myself; that where I am, there ye may be also.
I the Lord have called thee in righteousness, and will hold thine hand, and will keep thee, and give thee for a covenant of the people, for a light of the Gentiles;
Jesus is the covenant promised that would not fail.
Matthew 28:20 Teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you alway, [even] unto the end of the world. Amen.
I have learned that actually all the promises are conditional. There is always someone responsible to the covenant agreement. For example, In the case of the rainbow after the flood it was an agreement through Noah that extends to us. The Abrahamic covenant extends to all of us who take on Christ As sons and daughters of God. All reflect upon the ultimate covenant from the Father with the Son Jesus Christ for us.
But what God says he will do, he will definitely do.
So for example, when there is no covenant agreement with fallen beings, it is just God and that object, and since the object cannot break the covenant, God will definitely carry it out.
This famous place comes to mind:
Genesis 8:21 And the LORD smelled a sweet savour; and the LORD said in his heart, I will not again curse the ground any more for man's sake; for the imagination of man's heart [is] evil from his youth; neither will I again smite any more every thing living, as I have done.
22 While the earth remaineth, seedtime and harvest, and cold and heat, and summer and winter, and day and night shall not cease.
But yes, when covenanting with fallen beings, it looks to me too that pretty much everything is conditional.
