Place the onion and garlic in the bottom of a large slow cooker. Pour chicken broth over the onions and garlic.
In a small bowl, stir together brown sugar, chili powder, salt, cumin, paprika, garlic powder, and onion powder.
Pat the pork dry with paper towels. Rub the spice mixture all over the pork and place the meat on top of the onions and garlic. Cover and cook until the pork is fall-apart tender, about 5-6 hours on HIGH or 10-12 hours on LOW.
Turn off the slow cooker and remove the pork to a cutting board. Use two forks to shred the meat, discarding any large pieces of fat. Return the meat to the juices in the pot. Taste and season with salt and pepper, if desired.
Serve the pulled pork on sandwich rolls, on salad, or stuffed into baked potatoes. Spoon bbq sauce over top!