Trim any excess fat from the pork shoulder and cut the meat into large chunks.
In a small bowl, whisk together the chili powder, ground cumin, garlic powder, onion powder, sea salt, and black pepper.
Rub the spice mixture thoroughly onto all sides of the pork chunks.
Place the seasoned pork and water into a slow cooker; cover and cook on low for 7-8 hours or high for 4-5 hours until the meat is tender enough to pull apart.
Remove the pork from the slow cooker and shred it using two forks, discarding any remaining large pieces of fat.
Heat a large non-stick skillet over medium-high heat and add the shredded pork, pressing it down with a spatula to sear for 3-4 minutes until the edges are golden and crispy.
Warm the corn tortillas in a separate dry pan or directly over a low gas flame for 30 seconds per side until pliable.
Thinly slice the radishes and roughly chop the cilantro.
Divide the crispy pork evenly between the two tortillas and top with the sliced radishes, cilantro, and a fresh squeeze of lime juice.