Powers and power levels of Arda beings

[Nerwen]

No offence, Gorthaur, but I think a lot of this is unanswerable, largely because you talking about "power" as though it's a singular, measurable quality, like height.

Do you mean– Strength of will? Physical strength? Intelligence? Fighting skill? Magical ability?

Example:

Originally Posted by Gorthaur the Cruel

4. How powerful was Dior? It seems to me that he was more powerful than his mother, having killed three of Feanor's sons. And they were Calaquendi as well. Impressive considering that the sons of Feanor chased away the Balrogs who slew their father. Was it his maiarin blood at work here? If so, how was he able to inherit it if Luthien became "mortal" before he was conceived? Shouldn't he just be a regular man, unless Luthien, then an elf, mated with Beren before their deaths and ressurection?

Luthien wasn't a warrior and never killed anyone at all. Dior, as far as I can recall, never cast any spells. Asking which was "more powerful" is like taking a runner and a chessplayer and asking "who wins?" without specifying the contest.

As for the other question: yes, it's something that Dior was able to kill the Sons of Feanor– however, Luthien didn't cease to be Melian and Thingol's daughter by becoming mortal. She chose to be subject to a finite lifespan, and a different fate after death from the Elves, but I don't think that implies she literally turned into a garden-variety human, genetics and all. In fact, Tolkien makes a number of pretty unambiguous statements to the contrary, e.g.

[Dior] appeared as the fairest of all the children of the world, of threefold race: of the Edain, of the Eldar, and of the Maiar of the Blessed Realm.

I mean, I should think that if that only came about because Luthien was already pregnant with Dior when she died (the first time), the fact would would have rated a mention somewhere. Seems like an important point to leave out altogether.