nothing if not

nothing if not (something)

Most characteristically (something); (something) more than any other thing. In this phrase, "not" is always followed by a modifier of some kind that is emphasized as the most prominent attribute. He's nothing if not generous—that's his third donation this week. I am nothing if not patient, but even I have my breaking point.
See also: if, not, nothing
Farlex Dictionary of Idioms.

nothing if not

Above all else, as in He was nothing if not discreet. Shakespeare used this idiom in Othello (2:1): "I am nothing if not critical." [c. 1600]
See also: if, not, nothing
The American Heritage® Dictionary of Idioms by Christine Ammer.
See also:
  • nothing if not (something)
  • nothing if not something
  • high old
  • dye
  • dye in the wool
  • par excellence
  • out-and-out
  • ever so
  • ever so/ever such...
  • natural-born