First, I recommend buying a rotisserie chicken over shredding your own. It's easier and will make the recipe faster.
In a large pot or dutch oven on medium high heat add a little oil then toss in diced onion and Rotel tomatoes. Now, cook until the onions become translucent then toss in the minced garlic.
Once the garlic is fragrant, add in the corn and black beans. Now, pour in the packets of taco seasoning.
Mix everything together then add in chicken and chicken broth. Bring to a boil then lower to a simmer for 10 minutes. This is enough time for the taco seasoning to do its thing.
Add in chunks of velveeta cheese and allow the cheese to melt into the soup. Once cheese has melted remove the pot from the heat and turn off the stove.
Lastly, taste for seasoning, but you should be fine. Serve with cilantro, cheese, avocado or lime. Anything you typically enjoy with your taco soup will be great here or eat it as is.