Rub the pork shoulder with chili powder, cumin, garlic powder, sea salt, and black pepper until evenly coated.
Place the seasoned pork in a slow cooker and cook on low for 8 hours until the meat is tender and easy to shred.
Transfer the pork to a cutting board and shred into small pieces using two forks, removing any large pieces of fat.
Heat the avocado oil in a large skillet over medium-high heat until shimmering.
Add the shredded pork to the skillet in a single layer and sear for 3-5 minutes without stirring until the edges are golden and crispy.
Drizzle the fresh lime juice over the crispy pork and toss well to combine all the savory flavors.
Briefly warm the corn tortillas in a separate dry pan over medium heat for 30 seconds per side until soft and pliable.
Assemble the tacos by filling the warm tortillas with the crispy pork and topping with avocado slices, diced red onion, and fresh cilantro.