Which word describes someone who is incapable of being conquered?

The word "indomitable" is used to describe someone who cannot be defeated or subdued, signifying an unconquerable spirit. It conveys a sense of resilience and strength that enables a person to withstand challenges, opposition, or adversity without yielding. This quality is often admired in individuals who show unwavering determination in the face of difficulties, making "indomitable" the most suitable choice for someone incapable of being conquered.

In contrast, the other terms focus on different attributes: "infallible" refers to someone who is incapable of making mistakes or being wrong, "truculent" describes a person who is eager to argue or fight, often displaying aggressive behavior, and "virulent" generally pertains to something that is extremely harmful or destructive, particularly in the context of viruses or diseases. None of these words capture the essence of being unconquerable as effectively as "indomitable."