Heat oil in a large saucepan or dutch oven over medium heat and add the onion and garlic. Cook, while stirring, until the onions are translucent, about 3 minutes.
Stir in the red pepper and the jalapeño (use 2 Tbsp if you like a little heat and 1 Tbsp if you prefer mild) and cook for about 10 more minutes. Stir in the chili powder, cumin, oregano, salt, and pepper and cook for another two minutes.
Add sweet potatoes, water, diced tomatoes, tomato paste, black beans, and kidney beans to saucepan. Bring mixture to a boil. Once boiling, lower to a simmer, cover, and cook it until the sweet potatoes are tender, about 25 minutes.
Serve and garnish with avocado and cilantro if desired.