I think that Arnold Friend could be seen as a devil- like figure through his appearance.  On one hand, Friend's appearance is one where he wishes to look younger than he actually is.  The duplicity here feed the idea of him being devil- like because of the temptation element.  In seeking to lure another, the devil would appear to be something he is not.  In this case, Friend's use of makeup and style helps to make him appear "hip" or "cooler" than he really might be.  The use of fashion and his yellow jalopy also help to convey that he might be devil- like, as the use of flash and a stylistic chariot helps to convey this.  The "X" as his symbol is kind of devilish in its intent, something that communicates threat and fear.  The fact that Arnold speaks to Connie in such a comforting and connective way and then turns to threats in order to get what he wants can be another instance where his devil- like nature is revealed.  For Arnold, what is not gained through flattery is gained through coercion.  At the same time, the entire atmosphere communicated in the ending that going with Arnold is akin to Connie entering a world of void or emptiness is another element in which some aspect of a darker world is communicated.  In these instances, Arnold Friend can be seen as an example of the devil.