This is the 14871st most frequent German word.
regelrechter
"Regelrechter" means "literal" or "outright" in English, often used to emphasize something as fully or truly being the case.
Here, 'regelrechter' intensifies 'Albtraum', meaning a literal and extreme instance.
Das war ein regelrechter Albtraum.
That was a downright nightmare.
In this context, 'regelrechter' adds emphasis to 'Experte', implying genuine expertise.
Er ist ein regelrechter Experte auf diesem Gebiet.
He is a real expert in this field.
Here, 'regelrechter' emphasizes 'Erfolg', indicating the success was noteworthy and definitive.