In a large bowl, combine the shredded chicken, refried beans, cheddar cheese, chili powder, cumin, garlic powder, onion powder, salt, and black pepper. Mix until well combined.
Lay a tortilla flat on a clean surface. Spoon about 1/2 cup of the chicken mixture onto the center of the tortilla.
Fold the sides of the tortilla over the filling, then roll it up tightly from the bottom to the top, ensuring the filling is sealed inside. Repeat with the remaining tortillas and filling.
Heat the vegetable oil in a large skillet over medium-high heat.
Once the oil is hot, carefully place 2-3 chimichangas in the skillet, seam side down. Fry for about 3-4 minutes on each side, or until golden brown and crispy.
Remove the chimichangas from the skillet and place them on a paper towel-lined plate to drain excess oil.
Serve hot with sour cream and salsa on the side.