Rinse the dried kidney beans and pinto beans under cold water and remove any debris. Soak the beans in 3 cups of water overnight or for at least 8 hours. Drain and rinse before using.
Heat olive oil in a skillet over medium heat. Add diced onion and cook until translucent, about 5 minutes.
Add minced garlic to the skillet and cook for 1 minute until fragrant.
Add ground beef to the skillet and cook until browned, breaking it up with a spoon, about 7 minutes. Drain excess fat.
Transfer the browned beef, cooked onions, and garlic to the slow cooker.
Add soaked and drained beans, diced tomatoes (with juice), tomato paste, and beef broth to the slow cooker.
Stir in chili powder, ground cumin, smoked paprika, dried oregano, salt, black pepper, and cayenne pepper until well combined.
Cover the slow cooker and cook on low for 8 hours, or until beans are tender and chili is thickened.
Stir the chili before serving. Adjust seasoning with additional salt or chili powder if desired.