Step 1: In a large skillet, heat 1 tablespoon of olive oil over medium-high heat. Add the ground beef and cook, breaking it apart with a spoon, until fully browned. Drain off any excess grease. Transfer the browned beef to your 6-quart (or larger) slow cooker.
Step 2: To the same skillet (no need to clean it!), add the chopped onion and bell peppers. Sauté for 5-7 minutes until softened. Add the minced garlic and cook for another minute until fragrant.
Step 3: Add the sautéed vegetables to the slow cooker with the beef. Stir in the chili powder, cumin, smoked paprika, dried oregano, and cayenne pepper (if using). Add the tomato paste, diced tomatoes, crushed tomatoes, beef broth, rinsed kidney beans, and rinsed pinto beans. Stir everything well to combine.
Step 4: Cover the slow cooker with its lid. Cook on low for 6-8 hours or on high for 3-4 hours.
Step 5: About 30 minutes before serving, stir in the frozen corn. Taste the chili and season with salt and freshly ground black pepper to your preference.
Step 6: Once the corn is tender and the flavors have fully developed, your chili is ready. Ladle generously into bowls.
Step 7: Serve hot with your favorite toppings such as shredded cheddar cheese, sour cream, chopped green onions, fresh cilantro, or diced avocado.