Add the black beans, kidney beans, pinto beans, onion, green bell pepper, red bell pepper, and garlic to the slow cooker.
Pour in the crushed tomatoes and vegetable broth.
Sprinkle the chili powder, cumin, smoked paprika, salt, and black pepper over the top.
Stir everything together until the spices are evenly distributed.
Cover and cook on low for 6 to 7 hours.
Taste and adjust salt if needed before serving.
Ladle into bowls and add optional toppings if desired.