der Killer
killer
A person who kills someone, especially a contract killer.
Im Film wird ein ehemaliger Agent von einem unbekannten Killer gejagt.
In the film, a former agent is hunted by an unknown killer.

killer
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killer
A person who kills someone, especially a contract killer.
Im Film wird ein ehemaliger Agent von einem unbekannten Killer gejagt.
In the film, a former agent is hunted by an unknown killer.

The original meaning 'Mörder' (murderer) is literal. The meanings 'etwas Tolles' (something great) or 'etwas Störendes' (something disruptive), on the other hand, are colloquial and are used only in informal conversations.
Die Polizei sucht nach einem professionellen Killer.
The police are looking for a professional killer.
In the meaning 'Mörder' (murderer), 'Killer' (killer) is often used as part of compound words to specify the type of killing, for example 'Auftragskiller' (contract killer) or 'Serienkiller' (serial killer).
Der Roman handelt von der Jagd auf einen gerissenen Serienkiller.
The novel is about the hunt for a cunning serial killer.
When 'Killer' (killer) describes something very good or impressive, it is a strongly colloquial expression often used by younger people. It expresses extreme enthusiasm.
Das Konzert gestern war der Killer!
The concert yesterday was a killer!
In the meaning 'etwas, das stört' (something that disrupts), 'Killer' (killer) is often used with the preposition 'für' (for) and a noun in the accusative. This construction describes exactly what is being prevented or destroyed.
Ständige Unterbrechungen sind der Killer für kreatives Arbeiten.
Constant interruptions are the killer for creative work.
hammer
'der Hammer' and 'der Killer' can both express in colloquial speech that something is extremely strong, good, or impressive. 'der Hammer' is broader and fits many strong reactions, positive or sometimes also negative. 'der Killer' sounds harsher and is often used when something is especially effective or destroys, ends, or seriously harms something else. For that reason, the words are not always interchangeable. For general excitement, 'der Hammer' is more natural. When something has a strong effect or pushes something else aside, 'der Killer' fits better.

Für das Projekt ist diese neue Idee ein echter Killer, weil sie viel Zeit spart.
This new idea is a real killer for the project because it saves a lot of time.
Die Aussicht am Meer ist wirklich der Hammer.
The view by the sea is really amazing.