^^^ What she said. Nice job.Depends on what side of the dark you mean.
I've seen and heard NF's be extremely manipulative and self-absorbed, to the point of throwing tantrums to get their way, habitually cheating on SO's, and being really self-deceptive. As in hiding being this mask of feeling superior to others because they are so omniscient or 'so good at manipulating people' when really they are really afraid of people and unsure of themselves.
Then there are ENFPs who go overboard trying to people please and sacrifice their Fi or lose a solid hold on values in order to appease everyone.
So ENFPs can both be doormats or users depending on which dark side you mean.
Another darkside is ENFPs lapsing into a peter pan syndrome or running on pure Ne/fear of deprivation. Classic dark side Enneagram 7 as well (which correlates with ENFP), go to excess, become extremely irresponsible, can't keep a plan or thought or relationship for more than a few moments, running from high to high.
Another dark side of ENFP is getting overly zealous and reactive - not unlike an unhealthy INFP (though I think INFPs are worse in this way...lol, just sayin!) Digging in your heels just to be contrary and because you take it as a personal attack that someone is criticizing something you have said or done. The shadow ENFP in this case is entirely reactive and feeling under attack fromthe world.