ULPT request: How to cost large companies money?

So at work we mostly deal with other businesses. Today I found out this business that screwed over one our clients by claiming ignorance probably did it on purpose. I’m not a lawyer but I am 99% sure my client has a pretty good case against them for at least negligence at the very least. It would be like if I sold you my house but then forgot to give you the keys until after you hired a locksmith. Anyways my client doesn’t want to go after them because they are a huge corporation and don’t have the money to fight them. This happened months ago but today I found an article that basically says their MO is to screw over any competitors any way they can. Nothing too illegal or obvious I’m just one guy.