A Complementary Quine
Retina, 2 1 byte

P


Outputs

0


Explained

P actually has no special meaning in retina, but retina treats it like a regex against the input, and counts the matches. As there's no input, there's no matches, so it returns 0, which is the exact inverse of this.

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This is using an older version of Retina, which outputs a newline with the zero. This is not the case in the latest version.