The phrase "complete impossibility" is correct and commonly used in written English.
It refers to something that is absolutely impossible and cannot be achieved under any circumstances. Example: It was a complete impossibility for her to reach the top of the mountain without proper climbing gear.
Bellucci is unlikely to be a major threat to lead an upset unless the tie is played on clay, an almost complete impossibility given that the United States, as hosts, will select the surface.
But, noting his son's "remarkable appointments" and landslide re-election in 2008, he added, "When people say I've orchestrated some of these things, it's a complete impossibility to have great achievements like that from a father".
If sold at the previously rumored $18 billion mark, Twitter would be a big bite for Snap to swallow, but not a complete impossibility.
As media maven Geoff Golberg pointed out, however, taking a selfie with Spectacles is a complete impossibility.
Yet a population that lived through the September 11th attacks can scarcely ever confuse remote likelihoods with complete impossibilities.
Not just because I was short, Jewish and nerdily bespectacled by the time I was 8. No, it was something more enigmatic than that, and even less changeable: Even as an 8-year-old, I sensed the complete and irrevocable impossibility of anyone who rode the D train ever becoming Miss America.
She layers contrapuntal voices to evoke every family's aspirations to complete harmony and the impossibility of achieving it.
Others recognized the impossibility of complete objectivity.
The anatomical complexity of dental root canals represents a major limitation for a successful endodontic treatment, due to the impossibility of complete instrumentation.
13 patients (20%) had initial endoscopic treatment of the disease; nonsurgical oncological therapy had been indicated due to the impossibility of complete resection of the tumor or because patients rejected radicalization procedures.
