Pertinacious, Onerous

Pertinacious- holding tightly to a purpose; resolute; determined

Ex: The pertinacious bookstore worker spent most of his hours on the clock color coordinating the shelves so that the books’ spines, when viewed altogether, formed an image of a Romulan Warbird spacecraft from Star Trek: The Next Generation. Were a customer to mess with this mosaic, the worker would appear in extreme distress, as if an incomplete rendering of the spacecraft was not just an affront to his meticulously enacted artistic vision, but also a physical blow that dealt him real, tangible damage, causing him to writhe about on the bookstore’s floor like an earthworm caught in the sunlight. The worker also had difficulty making eye contact with customers, and he appeared overly sensitive to bright lights and loud noise. Although if you asked him to remember the release date of any particular Star Trek episode, he would rattle off the exact day, nay, the hour in which it was first broadcast. The worker’s boss thought to himself that it was peculiar that most people he knew who loved Star Trek presented many of the same behavioral symptoms.  

Onerous- very difficult to do; burdensome

Ex: He was tasked with the onerous job of keeping things civil in the early morning hours at the Waffle House. With all the liquored-up cretins and low-life booze bags that frequented the Waffle House after a night on the town, it was a miracle if a single night passed where not one video of a patron getting clapped on the back of the head with a waffle iron made it on to WorldStar.