1 pound ground beef
1/2 teaspoon crushed red pepper flakes, or to taste
1 teaspoon minced garlic
1/2 large onion, diced
1 green bell pepper, chopped
1 red bell pepper, chopped
1 (15 ounce) can kidney beans, rinsed and drained
1 (15 ounce) can black beans, rinsed and drained
1 (15 ounce) can Great Northern beans, drained and rinsed
1 (8 ounce) can tomato sauce
1 (5 ounce) can tomato sauce with garlic and onions
2 (14.5 ounce) cans petite diced tomatoes
1 (14.5 ounce) can fire roasted diced tomatoes
1 (15 ounce) can pumpkin puree
2 teaspoons pumpkin pie spice
2 teaspoons chili powder
1 teaspoon ground cumin
1 teaspoon salt, or to taste
Heat a large skillet over medium-high heat; cook and stir the beef in the skillet until crumbly and no longer pink, about 5 minutes. Stir in the red pepper flakes, garlic, and onion; continue cooking until the beef has browned and the onion has softened and turned translucent. Add the green and red bell pepper and cook 5 minutes more.
While the beef is cooking, combine the kidney beans, black beans, Great Northern beans, tomato sauce, tomato sauce with garlic and onions, petite diced tomatoes, fire roasted diced tomatoes, and pumpkin puree in a large slow cooker. Season with pumpkin pie spice, chili powder, cumin, and salt. Stir in the ground beef mixture.
Cook on Low until the chili is hot, 1 to 2 hours.