Green’s Dictionary of Slang

fanfuckingtastic adj.

[SE fantastic + fucking adj. (4)]

extremely fantastic, an intensified form of SE.

[Can]M. Atwood Cat’s Eye (1989) 280: ‘It sucks,’ they say, or very occasionally, ‘fan-fuckin’-tastic.’.
[UK]K. Lette Mad Cows 6: Fan-fucking-tastic, whinged Maddy to a morose flock of tuxedoed penguins advertsing the freezer section.
[US]C. Hiaasen Lucky You 98: ‘Not jes good,’ said his ponytailed friend, ‘fan-fucking-tastic!’.
[UK]N. Barlay Crumple Zone 146: Fanfuckintastic acoustics.