Antagonist
Character Role Analysis
Existence
Seriously, there's really no enemy in this book apart from the world of physical objects that always seems to be closing in around Antoine. He tries to push them back and to avoid the feelings of nausea that they cause, but with little success.
At the end of the day, existence is always staring at Antoine, tormenting him and making him sick to his stomach. It's not until he finally reconciles him to the harsh truth of a meaningless universe that Antoine is actually able to live among things—like tables—with some level of comfort.