At the bottom of a large Dutch oven, place the sliced onions, garlic and then the pork butt, with the fatty side facing up.
Mix the spices together and spread them all over the pork. Pour the chicken broth into the bottom of the pot. Tightly cover and bake for 4 hours.
With 2 forks, shred the pork, and stir in the sugar.
For the Grilled Pineapple Salsa:
Grill the pineapple on an indoor grill pan, until it softens a little. Mix the pineapple with all the other ingredients.
To assemble the Nachos:
Mix the beans with the spices and warm them up until they're hot.
Place the tortilla chips on a baking sheet, top with the cheese, and broil until the cheese is melted. Top the tortilla chips with the black beans, pulled pork, salsa, sour cream, and guacamole.