Did Melkor really mar creation?

[metropolis_part_one]

I thought it was his presence that made the world so beatiful, for example, he created the Misty Mountains, the icy wastes and the firey pits. Surely he enhanced the world by creating conflict and drama too, for if he had not the world would be intolerably boring?

[Gil-Galad]

Like most nations today, the ydo not want violence or war or anything thats will hamr them... and it was Aule that made the mountains, Melkor just wanted to rule and ahted the elves

[Finwe]

During the Ainulindalë, Iluvatar singled Morgoth out, and told him that all of his desires would have their uttermost source in him (Iluvatar), and that no matter what he did, or how much he rebelled, all his actions would follow Iluvatar's higher purpose for the world.

Keeping that in mind, wouldn't some things that Morgoth created have been beautiful? Granted, the dungeons of Angband couldn't have been what we would call "beautiful," but they did ultimately adhere to Iluvatar's "higher purpose," though we know not what that is.

[Lord of Angmar]

Ulmo: Thus even as Eru spoke to us shall beauty not before concieved be brought into Eä, and evil yet be good to have been.

Mandos: And yet remain evil.

[Man of the Old Hope]

I think this passage from a draft of a letter to Peter Hastings (153 in The Letters of J.R.R. Tolkien) gives us some idea of how Tolkien viewed Melkor's "creative" power:

"So in this myth, it is 'feigned' (legitimately whether that is a feature of the real world or not) that He gave special 'sub-creative' powers to certain of His highest created beings: that is guarantee that what they devised and made should be given the reality of Creation. Of course within limits, and of course subject to certain commands or prohibitions. But if they 'fell', as the Diabolus Morgoth did, and started making things 'for himself, to be their Lord', these would then 'be', even if Morgoth broke the supreme ban against making other 'rational' creatures like Elves or Men. They would at least 'be' real physical realities in the physical world, however evil they might prove, even 'mocking' the Children of God. They would be Morgoth's greatest Sins, abuses of his high privilege, and would be creatures begotten of Sin, and naturally bad. (I nearly wrote 'irredeemably bad'; but that would be going too far. Because by accepting or tolerating their making - necessary to their existence - even Orcs would become part of the World, which is God's and ultimately good.)...I have represented Orcs as pre-existing real beings on whom the Dark Lord has exerted the fullness of his power in remodelling and corrupting them, not making them. That God would 'tolerate' that, seems no worse theology than the toleration of the calculated dehumanizing of Men by tyrants that goes on today. There might be other 'makings' all the same which were more like puppets filled (only at a distance) with their maker's mind and will, or ant-like operating under direction of a queen-centre." (emphasis added)

Two themes emerge here, and we can see at least the second in the Ainulindalë. First, the notion that Melkor/Morgoth's creative power is derivative and corrupting; and second, that even this corrupting power is ordered finally toward the purposes of Eru Ilúvatar: "And thou, Melkor, wilt discover all the secret thoughts of thy mind, and wilt perceive that they are but a part of the whole and tributary to its glory."

If there be any beauty whatever in Melkor's works, it is so only because of the thought and providence of Eru Ilúvatar.

[Earendilyon]

Although Morgoth contributed to the beauty of Arda, this was not his intention. He intended to destroy what the other Valar created, but by trying that, he contributed to how Arda became to look like. If he had cooperated with the other Valar, Arda would've looked different. I think it would have been even more beautiful, for Melkor was the most powerfull of the Valar and had knowledge of all the other Valar's skills. He could have greatly helped them.