The large corporation is a target customer and a potential competitor to other target customers.
I think you have to follow your gut here. If its telling you that this investor is going to be a more of a headache and will take up most of your time then don't take the investment. You want to make sure you are focused on building a great company.
I would also have a conversation about how the investor feels about you approaching their competitors as potential customers. Get it all out on the table before signing the dotted line.
