unnötig
unnecessary
Not necessary or required; superfluous.
Deine abfällige Bemerkung war in dieser Situation völlig unnötig.
Your disparaging remark was completely unnecessary in this situation.

unnecessary
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unnecessary
Not necessary or required; superfluous.
Deine abfällige Bemerkung war in dieser Situation völlig unnötig.
Your disparaging remark was completely unnecessary in this situation.

The adjective is made up of the negative prefix 'un-' and the adjective 'nötig' (necessary). So it literally means 'not necessary'.
Bitte machen Sie keine unnötigen Kopien.
Please don't make any unnecessary copies.
'Unnötig' can also be used as an adverb to modify a verb or another adjective. It then means 'in a way that is not necessary'.
Du hast die Situation unnötig kompliziert gemacht.
You made the situation unnecessarily complicated.
Often, 'unnötig' does not only express that something is superfluous, but also contains a negative judgment or criticism. An 'unnötige Bemerkung' (unnecessary remark) is usually also an inappropriate or hurtful remark.
Sein Kommentar über ihr Aussehen war verletzend und absolut unnötig.
His comment about her appearance was hurtful and absolutely unnecessary.
necessary
'nötig' and 'unnötig' form a clear contrast. 'nötig' is used when something is needed or important for a goal. 'unnötig' is used when something is not needed and can be done without. So the difference is simple: what is 'nötig' must or should be done or had. What is 'unnötig' brings no real benefit or is too much.

Wenn alle schon informiert sind, ist ein weiterer Anruf unnötig.
If everyone has already been informed, another call is unnecessary.
Für das Gespräch mit der Nachbarin ist ein ruhiger Ton nötig.
A calm tone is necessary for the conversation with the neighbor.