Walmart has competition. Target being one of them. I cannot remember the last time I stepped into a Walmart. I am sure you do not patronize them either! How will you go about " breaking up" Walmart?
My wife and I never go to Walmart because of the lines and there is nothing that they sell that we particularly want. Groceries we go to a regular grocery store since they have a better selection. Electronics we go to Best Buy because of Geak Squad. For music and movies we buy digital copies.
Their are certain things that only big business can do. Things that need to be mass produced to keep cost down etc. Their are things that only a small business can do mainly speciality things and personalized services.
The reason many big corporations pay low wages is really for two main reasons:
Any one can do the job in many cases. These are in many cases like Walmart and McDonald's etc jobs meant for teenagers.
Also why pay someone a living wage when the employee can go on welfare and the tax payers can make up the cost.