My go-to recipe for Taco Soup is from my Weight-Watchers days:
1 pound lean ground beef, at least 93% lean, browned
1 cup chopped onion (1 medium-size onion)
1 can (14 to 15 ounces) petite diced tomatoes, undrained
1 can (10 ounces) tomatoes with chiles, undrained aka Rotel
2 cans (14 to 15 ounces each) beans (kidney, pinto, black or chili), rinsed and drained (I use kidney and black)
1 can (11 to 15 ounces) corn, undrained
2 cups water
1 package (1.25 ounces) taco seasoning
I put all in my slow-cooker for 2 or 3 hours