Heat the vegetable oil in a large pot over medium heat until shimmering.
Add the chopped onion and cook, stirring occasionally, until it becomes translucent and soft, about 5 minutes.
Add the minced garlic and cook for 30 seconds more, until fragrant.
Stir in the ground beef, breaking it apart with your spoon, and cook until browned all over, about 7-8 minutes.
Add chopped bell pepper and cook for another 3 minutes until slightly tender.
Pour in the diced tomatoes with juices, stirring to combine all ingredients evenly.
Sprinkle in the cumin, cinnamon, chili powder, and season with salt and pepper, stirring well to evenly distribute the spices.
Bring the mixture to a gentle simmer, then reduce the heat to low.
Cover and let cook for 30-40 minutes, stirring occasionally, until the chili has thickened and flavors meld.
Stir in the drained kidney beans and cook for an additional 5 minutes to heat through.
Taste and adjust seasoning with more salt, pepper, or spices as desired.
Serve the chili hot in bowls, garnished with your favorite toppings such as shredded cheese, chopped cilantro, or sour cream if desired.