There is no noun like "der
Untergeher" in German.
There is
1. the verb "untergehen"
(= "sink" as in "das Schiff
sinkt" or "perish" as in "das Römische Reich ist
untergegangen")
2. the noun "Untergang"
(= "shipwreck as in "der Untergang
der Titanic" or "decline" as in "der Untergang des
Römischen Reichs")
So the "Untergeher" is "the one
who perishes" or in a mimetic translation (of which I don't know if it
works) "the perisher" or "the
failurer".
"The Loser" is not half as
devastating as "The Untergeher".
Some EUR 0,02
Jost