The high interest rates - especially what CC companies label "default rates" are what I see as the biggest problem. I have long been bothered by interest rates which not all that long ago would have been criminally prosecuted under loan sharking laws. I think the law should be adjusted to a limit of about 10% above prime rate. By tying it to the prime rate the way variable rate lenders do, the law would not need to be adjusted constantly for unusual economic conditions such as high inflation.
I also believe laws should be written to limit the reasons and circumstances under which a lender can change their rate. For instance, if a company decides it is essential that they go from prime+6 to prime +7 on certain accounts, they cannot, under any circumstances, apply that rate to balances outstanding at the time of the increase. The idea that if the credit account is used again, the new rate is applied to the entire balance it BS. And rate changes on variable interest loans should be limited to 1 time per year.
Also, there needs to be limits on what circumstances define a default which results in going to default penalties and default interest rates. Currently there are companies that switch to their default rate if an account receives a minimum payment for 4 months in a row - even if those payments are on time. That should be criminal. Default should be defined as missing 3 payments in a row, or more than 5 payments in a year later than 15 days. Lenders could, if they desired, be more lenient than that, but not more strict.
As for merchant credit, and the phenomenon of enticing customers with rewards for applying for credit, I do not see that as a problem government should be involved with - except to the extent of fraud prevention. People who just "gotta have it now" don't need a mothering government to watch out for them - they need to learn to watch out for themselves.
About the only regulation I would desire there is the print on the contract has to be the same size all through. No ultra fine print you need a microfiche reader to see.