A friend is trying to ruin the rest of my life and put me in debt. Help me?

I have a friend who came and asked me to co-sign for credit cards for hundreds of thousands of dollars for his business. At first I agreed and he said we would draw up a contract. After some more thinking, I realized I could not put myself in a position to ruin the rest for my life. He then provided me in an email for breach of oral contract since we didn't sign a written contract. I didn't sign any loan contracts or anything. They never even signed the stock over like they told me they would. Do u have a case to fight it since it was not a written contract and no loan contract was ever signed. So there's no way they could have anticipated money if they didn't know if they were getting any because no contract for loan or anything was signed