Set the Instant Pot to saute mode and add the olive oil. Add the ground beef and diced onion, cooking and breaking the meat apart for 5 to 6 minutes until the beef is browned and the onion is softened. Drain any excess grease.
Add the garlic and cook for 30 seconds. Stir in the taco seasoning and cook for another 30 seconds until fragrant.
Add the diced tomatoes with their juices, black beans, kidney beans, corn, diced green chiles, beef broth, and tomato sauce. Stir everything together until well combined.
Lock the lid and set the valve to sealing. Pressure cook on high for 10 minutes.
When the cook time is complete, allow a natural pressure release for 5 minutes, then carefully switch the valve to venting. Remove the lid once the pin drops.
Stir the soup and taste for seasoning, adding more salt if needed. Ladle into bowls and top generously with shredded cheddar cheese, a dollop of sour cream, crushed tortilla chips, fresh cilantro, and diced avocado.