Is it true that using scratched Teflon-coated pans contain carcinogens, and if so, can they be consumed through the food cooked in them?

E.g.


The deadly toxins from non-stick frying pans



Question: Word for a result/achievement so exceptional that it is impossible?
Answer: Unassailable sounds like it might fit the bill.


  
  Impossible to dispute or disprove; undeniable: unassailable truths.
  Not subject to attack or seizure; impregnable: an unassailable fortress.
  


thefreedictionary.com



Example sentence: 


  Liverpool football club are still looking unassailable.


Which is synonymous with:


  Defeating Liverpool football club still looks impossible.