Heat your pot over medium-high heat and add the ground beef. Break it apart with a wooden spoon and cook for 6-8 minutes until fully browned with no pink remaining. Drain off any excess fat by carefully tilting the pot and spooning out the grease, or pour everything through a colander set over a bowl.

Return the pot to the heat and add the diced onion directly to the cooked beef. Sauté for 3-4 minutes, stirring occasionally, until the onion becomes translucent and fragrant.

Add both cans of kidney beans, the pinto beans, corn, both types of diced tomatoes (with their juices), and the condensed tomato soup. Stir in the taco seasoning packet and 1 cup of water. Mix everything thoroughly for about 30 seconds until the seasoning is distributed evenly and no pockets of dry seasoning remain.

Bring the mixture to a rolling boil over high heat, then immediately reduce the heat to low. Cover the pot and let it simmer for 15-20 minutes, stirring every 5 minutes to prevent sticking. The soup will thicken slightly to a hearty, stew-like consistency.

Taste and adjust seasoning with salt and pepper as needed. Ladle into bowls and serve hot with your favorite toppings such as shredded cheese, sour cream, crushed tortilla chips, or fresh cilantro.