Heat 2 tablespoons olive oil in a large pot over medium heat. Add 1 cup chopped onion and 1/4 cup chopped red bell pepper and sauté until the onion is translucent, stirring occasionally.
Add 48 ounces marinara sauce, 16 ounces crushed tomatoes, and 1/4 cup finely chopped hot cherry peppers to the pot. Increase heat until the sauce begins to bubble, then reduce to low to maintain a gentle simmer.
While the sauce comes to a simmer, brown 1 pound ground beef and 1 pound ground Italian sausage in a separate large skillet over medium-high heat, breaking the meat into pieces as it cooks until no pink remains.
Drain any excess fat from the skillet, then transfer the browned meats to the pot with the simmering sauce.
Add 1/2 cup finely chopped pepperoni and 1 teaspoon Italian seasoning to the sauce, stir to combine, and continue to simmer, uncovered, for about 20 minutes, stirring occasionally.
While the sauce simmers, cook 1 pound dry thick spaghetti according to the package instructions in a separate pot; drain the spaghetti when done.
Taste the sauce and add salt and pepper to taste. Serve the sauce over the cooked spaghetti.