dummerweise
unfortunately
Expresses that something happened in an unlucky, clumsy, or annoying way.
Ich habe dummerweise meinen Schlüssel in der Wohnung vergessen.
Unfortunately, I left my key in the apartment.

unfortunately
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unfortunately
Expresses that something happened in an unlucky, clumsy, or annoying way.
Ich habe dummerweise meinen Schlüssel in der Wohnung vergessen.
Unfortunately, I left my key in the apartment.

The word is made up of the adjective 'dumm' (stupid) and the suffix '-weise' (-wise / in a way). It literally means 'in a stupid way' and expresses annoyance or regret about a mishap.
Er hat den Zug dummerweise um eine Minute verpasst.
Unfortunately, he missed the train by one minute.
As an adverb, 'dummerweise' (unfortunately) can stand in position 1; then the verb follows immediately. It can also stand after the verb in the middle of the sentence.
Dummerweise war der Supermarkt schon geschlossen.
Unfortunately, the supermarket was already closed.
With 'dummerweise' (unfortunately), the speaker comments on an event as unlucky or annoying. It adds a personal, often slightly self-critical or ironic note to the sentence.
Ich habe die Rechnung dummerweise schon bezahlt, bevor ich den Fehler bemerkte.
Unfortunately, I had already paid the bill before I noticed the mistake.
unfortunately
'leider' and 'dummerweise' both show that a situation is not good. 'leider' is more neutral and fits many kinds of bad or sad news. 'dummerweise' sounds more like annoyance, bad luck, or a clumsy mistake. It is often used when something goes wrong because of a foolish coincidence or a small oversight. So 'leider' is more general, while 'dummerweise' fits situations where you think: that could have gone better.

Zu Hause habe ich dummerweise den Schlüssel im Auto gelassen.
Unfortunately, I stupidly left the key in the car at home.
Im Zug gibt es leider keinen freien Sitzplatz mehr.
Unfortunately, there are no free seats left on the train.