Which factor is MOST likely to reduce an individual's credit score?

Maxing out credit card limits is the factor that is most likely to reduce an individual's credit score. Credit scoring models take into account the credit utilization ratio, which is the amount of credit being used compared to the total amount of credit available. When an individual maxes out their credit cards, they are using a high percentage of their available credit. This high utilization rate can be seen as a sign of financial distress or over-reliance on credit, which negatively impacts the credit score.

Maintaining a lower credit utilization ratio, ideally below 30%, indicates that a person is using their credit responsibly and is less likely to default on payments. This responsible usage can help maintain or even improve a credit score over time. In contrast, maxing out credit cards can convey financial strain, leading to a drop in the credit score.