Breakdown of Der Erfolg ist diese unnötige Qual nicht wert.
sein
to be
nicht
not
dieser
this / that (fem.: diese, neut.: dieses)
der Erfolg
the success
Questions & Answers about Der Erfolg ist diese unnötige Qual nicht wert.
Why is diese unnötige Qual in the accusative case?
The adjective wert (worth) belongs to a small group of German adjectives that strictly require an object in the accusative case. Because the success is not worth "this unnecessary agony", the phrase diese unnötige Qual acts as that accusative object.
Why is wert placed at the very end of the sentence?
Adjectives that govern an object usually go at the end of the clause. The object (diese unnötige Qual) and the negation (nicht) must come before the adjective (wert) that controls them. You cannot say nicht wert diese unnötige Qual like you would in English.
I often confuse accusative endings. Why doesn't the adjective unnötige end in -en here?
Because Qual is a feminine noun. In the accusative case, feminine adjectives following a demonstrative word like diese just take an -e ending. The -en ending you might be thinking of only applies to masculine nouns in the accusative.
How would this sentence change if I used a masculine noun, like Aufwand (effort), instead of the feminine Qual?
Because wert forces the accusative case, the masculine article and adjective would change to clearly show the accusative. The sentence would become: Der Erfolg ist diesen unnötigen Aufwand nicht wert.