Hurin the Wraith

[Kuruharan]

You have a good point about the nature of Morgoth's power over Hurin as opposed to Sauron's power over the Ringwraiths. However, this line is very difficult...

and never shalt thou move from this place until all is fulfilled unto its bitter end.

The Sil

This brings up the question of if Morgoth knew that Hurin's children would all be dead before the end of Hurin's own life. It has also occured to me that the reason why Morgoth let Hurin go is because Hurin was about to die anyway.

However, the above line does not cause nearly the problems as this one...

There he was bound by the power of Morgoth; and Morgoth standing beside him cursed him again and set his power upon him, so that he could not move from that place, nor die, until Morgoth should release him.

The UT

There may be a reason why this line was not included in The Sil. CT may have seen the problem or JRRT before him and decided that Morgoth's curse needed a little rewriting.