In a large skillet over medium heat, brown the ground beef until fully cooked, breaking it apart with a wooden spoon. Drain any excess fat.
Add the diced onion to the skillet and cook for about 3 minutes, until the onion is soft.
Stir in the diced pickles, Worcestershire sauce, ketchup, mustard, mayonnaise, garlic powder, onion powder, salt, and pepper. Mix well to combine all the ingredients.
Allow the mixture to simmer for 5-7 minutes, stirring occasionally, until heated through and thickened slightly.
While the filling is simmering, toast the hamburger buns if desired.
To serve, spoon the Big Mac sloppy joe mixture generously onto each bun. Top with shredded lettuce and cheddar cheese.
Close the sandwiches with the top half of the buns and serve immediately.