Heat the olive oil in a large skillet over medium-high heat until shimmering.
Add the ground beef to the skillet and cook, breaking it into small crumbles with a wooden spoon, until it is browned and no longer pink.
Carefully drain any excess fat from the skillet and transfer the browned beef into the slow cooker basin.
Add the rinsed kidney beans, tomato puree, diced onion, and diced green bell pepper to the slow cooker.
Sprinkle the chili powder, ground cumin, garlic powder, sea salt, and black pepper over the mixture.
Pour in the water and stir all ingredients thoroughly to ensure the spices are evenly distributed.
Secure the lid and cook on the low setting for 6 to 8 hours, or on high for 3 to 4 hours, until the flavors are deeply melded.
Ladle the hot chili into bowls and serve immediately.