Which Personal Auto Policy coverage will pay for the insured's injuries if injured by an at-fault third party with insufficient liability insurance?

Underinsured Motorist coverage is designed specifically to address situations where an insured is injured by a driver who has insufficient liability insurance to cover the damages resulting from an accident. This coverage steps in to fill the gap when the at-fault party's insurance limits are inadequate, ensuring that the insured can recover medical expenses, lost wages, and other damages that exceed the at-fault party's liability policy limits.

In contrast, Comprehensive coverage primarily protects against non-collision incidents, such as theft, vandalism, or natural disasters, and does not address bodily injury caused by other drivers. Medical Payments coverage provides benefits for medical expenses resulting from an accident regardless of who caused it, but it does not apply if the at-fault driver lacks sufficient insurance. Collision coverage covers damages to the insured's vehicle resulting from a collision, rather than addressing personal injuries sustained in an accident. Thus, Underinsured Motorist coverage directly satisfies the scenario described in the question, making it the correct choice.