Rinse the pinto beans in cold water and sort through them to remove any debris. Soak them overnight in water, or at least for 6 hours.
In a skillet over medium heat, heat 1 tablespoon of olive oil. Add the ground beef and cook until browned. Drain excess fat if necessary.
In the slow cooker, combine the soaked pinto beans, beef broth, diced green chiles (with their liquid), diced onion, minced garlic, chili powder, cumin, salt, and black pepper. Stir well.
Add the cooked ground beef to the slow cooker and mix everything together.
Cover and cook on low for 8 hours or until the beans are tender and the flavors melded.
In the last 30 minutes of cooking, add the corn to the slow cooker and stir well.
Once it's done cooking, taste and adjust seasoning if necessary.
Serve hot, garnished with chopped cilantro and avocado if desired.