A neatnik is someone who is very organized and clean, so the bane of a neatnik's existence would be anything that disrupts their order. The crossword solutions for this term are 'DUST', 'messes', 'MESS', 'CLUTTER', and 'SLOB'. DUST is a fine powdery substance that accumulates on surfaces, messes are chaotic arrangements of objects, MESS is another word for a MESS, CLUTTER is a disorderly collection of objects, and a SLOB is someone who is untidy and careless. All of these words describe things that would be the bane of a neatnik's existence.