Well, you have fvck, fsck (which is actually a *nix command), phuck, phuk, phuctard, phuktard, fock, f0ck, [email protected]
, fack, fick, ficken (which is a real German word), etc.
That's just ONE word. Don't get me started on shite and all its variants.
So in order to "properly" ban that word, you will also need to ban variants on the word. Eventually your filters will hit around 100 words.
It would SUCK to be the one typing all that in.