Add chipotle pepper, beans, tomato sauce, tomatoes, chilis, chili powder, cumin, salt, sugar, and pepper to slow cooker. Stir to combine.
Heat oil in a skillet over medium-high heat. Add beef and cook until browned, about 4-5 minutes. Transfer out of pan and place in slow cooker.
Add onion to the same pan and cook until softened, about 4-5 minutes.
Add garlic and cook until fragrant, stirring occasionally, about 30 seconds. Transfer onion and garlic out of pan and place in slow cooker.
Cover and cook for 3-4 hours on high or 6-8 hours on low.
