In "Dulce et Decorum Est," a simile that is used to describe the face of the gassed soldier is: -lime -devil -wagon -sin -none of these

Similes rather than metaphors predominate in the
description of the gassed soldier; the central one, as  the previous post identifies, is
His hanging face, like a devil's sick of sin as he lies in the
wagon containing the dead and dying.

It is crucial not just
to spot similes but to give explanations of how they work. This contains no less than 3 
other poetic techniques! Sick of sin is alliterative
and there is assonance allowing one to
almost spit out the words. Most importantly there is also contradiction,
oxymoron: how can a devil be sick of sin? The answer is
that it is only his face which is like a devil's, made hideous by the effects of the
gas. He himself is a man, sick of the evil of War.