This question also has an answer here (in German):
Schlussformel für Beschwerdebrief?
I am writing a complaint letter and want to know how to end it. The issue was pretty bad and I'm very unsatisfied/offended with the service, so does "Mit freundlichen Grüßen" sound ironic? (I'm definitely not freundlich in the letter).
Is there something more neutral like the English Regards or Sincerely?
Mit freundlichen Grüßen
orFreundliche Grüße
orHochachtungsvoll
. While your letter may sound unfriendly it is important to not be offending.