InFile='/usr/share/dict/words'
RW='etaoinshrldu'  # RW = Reference Word
echo "There are "$(wc -l <$InFile)" words in the InFile."

echo
echo '========================================================================='
echo 'Identify letters in each InFile word which are not in the Reference Word.'
echo '========================================================================='

echo; echo 'Method #1 of LQ Member danielbmartin.'
echo 'Reference Word = '$RW
time tr -d "[$RW]" <$InFile |paste -d' ' $InFile - >$OutFileA


echo
echo '========================================================================='
echo 'Now address the mirror-image problem....'
echo 'Identify letters in the Reference Word which are not in each InFile word.'
echo '========================================================================='

echo; echo 'Method #6.2 of LQ Member danielbmartin'
      echo '  using INDEX and MAWK as suggested by shruggy.'
echo 'Reference Word = '$RW
time mawk -v rw=$RW 'BEGIN{n=split(rw,a,"")}
          {NoMatch=""
           for (j=1;j<=n;j++)
             if (!index($0,a[j])) NoMatch=NoMatch a[j]
           print $0,NoMatch}' $InFile >$OutFileG

echo; echo "Normal end of job."; echo; exit

There are 99171 words in the InFile.

=========================================================================
Identify letters in each InFile word which are not in the Reference Word.
=========================================================================

Method #1 of LQ Member danielbmartin.
Reference Word = etaoinshrldu

real	0m0.012s
user	0m0.008s
sys	0m0.004s

=========================================================================
Now address the mirror-image problem....
Identify letters in the Reference Word which are not in each InFile word.
=========================================================================

Method #6.2 of LQ Member danielbmartin
  using INDEX and MAWK as suggested by shruggy.
Reference Word = etaoinshrldu

real	0m0.208s
user	0m0.204s
sys	0m0.000s

Normal end of job.