Final answer:
Unsecured credit cards with variable interest rates are generally considered the riskiest due to the lack of collateral and unpredictable borrowing costs.
Step-by-step explanation:
When considering which type of credit card carries the most risk, an unsecured credit card with a variable interest rate is typically seen as the riskiest option. Secured credit cards require a deposit, which reduces risk for the lender, but with an unsecured card, there is no such collateral. Furthermore, a variable interest rate can fluctuate, potentially increasing the cost of borrowing if the rate rises. Fixed interest rates provide more predictability over the borrowing costs.