The problem for Doffy here is not strength but hax, there are really nasty abilities that can kill you or worse in a moment in the HxH verse like the disasters brought back from the dark continent or Nanika powers (she is a reality warper on galaxy level at the very least yet her host, Alluka, is just a girl), let's say they are the HxH version of Sugar. Yet if we take it just powerwise Doffy should simply be too strong and fast for the HxH verse.