A hexpert can also mean someone who is really good at using standard-cinfigured bolts and nuts, but perhaps knows little about square-headed fasteners.
A person, usually a coworker, who's offering unsolicited and undesirable help, being more of a nuisance than a source of actual help.
That helperton insisted on bagging my groceries, and he put all of the heavy frozen foods in a single paper bag which ripped apart as I was carrying it out.
Da dire/gory hoped-for results of sticking pins into a voodoo doll, burning a candle with the mark's name on it, or carving a face on a tree and pounding a nail into the tree.