antōrren
the quality of having come to the natural point of completion of a process or an event, finished, ended.
The second part of yesterday’s noun phrase is antōrren. Since this is modifying the inanimate singular jacēha “attempt”, it is also inanimate singular. So in this sentence from the North Wind and the Sun, the thing which the North Wind is finally doing is ending its attempt at blowing the cloak off the wanderer.
illoren ñamma jacēha jatōrren ā mūrāna masīrien;
Finally, the North Wind stopped trying.
Is there word for an unnatural or forced completion of something?
Hmm. No. You could say something periphrastic, using the neutral anÅrre “stopped” to imply something stopped before natural completion and declared done anyway.