Tard may also be derived from 'turd' a word commonly used in place of 'shit'.
Fucktard can be especially usefull when the other guy keeps saying 'fuck' and you have to shove one up his ass. Combine with words for greater effect.
Guy #2: Kiss my fucking ass, you cocksucking, motherfucking, cunt lickin', dickshitting FUCKTARD!!!!
Guy #3: -----speechless-----
A person of unbelieveable, inexcuseable and indescribable stupidity. (Stupidity being defined as "knowing how and doing it wrong anyway")
NOT A CONTRACTION FOR "FUCKING RETARD"! Those who are truly "Retarded" are not responsible for their affliction. True Fucktards are 100% responsible for their situation and provide vast entertainment as they are usually blissfully unaware of their own Fucktardery. Most politicians for example.
He shot himself in the nuts? Geez, what a fucktard!