Heat the olive oil in a large heavy-bottomed pot over medium heat until shimmering. Add chopped onion and cook, stirring occasionally, until translucent and fragrant, about 5 minutes.
Add the minced garlic and cook for another minute, until it becomes fragrant and slightly golden.
Stir in the ground meat, breaking it apart with your spoon, and cook until browned on all sides, about 7-10 minutes.
Add chopped bell pepper and cook for 3-4 minutes until slightly softened and vibrant in color.
Pour in the diced tomatoes with juice, and add chili powder, cumin, and cinnamon. Stir well to combine all the spices evenly into the mixture.
Bring the mixture to a simmer, then reduce the heat to low and cover. Let it cook gently for 30 minutes, stirring occasionally to prevent sticking.
Uncover and stir in the drained kidney beans. Continue simmering uncovered for another 10 minutes to allow flavors to meld, stirring occasionally.
Add the chopped dark chocolate and stir until melted and fully incorporated into the chili, creating a glossy, rich sauce.
Taste the chili and season with salt and pepper as desired, then cook for another 2 minutes for flavor to settle.
Serve the chili hot, garnished with your favorite toppings if desired, and enjoy the layered, comforting flavors.