Brown ground beef with chopped onion until no longer pink. Drain grease well.
Combine the following ingredients in the slow cooker - Diced tomatoes, tomato sauce, ketchup, water, kidney beans, chili seasoning mix, chopped celery, Worcestershire sauce, and sugar. Stir together.
Add the browned hamburger/onion mixture in the slow cooker. Stir everything together.
Cook low for 6-8 hours or on high for 3-4 hours.
Top with shredded cheese and Frito's corn chips.
Notes
Once you are done cooking the chili, any leftover chili should be left to cool to room temperature and store the chili in an airtight container in the fridge for 4-5 days.