Courage

According to Western tradition:

"...the seven Christian virtues or heavenly virtues refers to the union of two sets of virtues. The four cardinal virtues, from ancient Greek philosophy, are prudence, justice, temperance (or restraint), and courage (or fortitude). The three theological virtues, from the letters of St. Paul of Tarsus, are faith, hope, and charity (or love).

Peter Kreeft:

The four cardinal virtues – justice, wisdom (prudence), courage (fortitude), and moderation (self-control, temperance) – come not just from Plato or Greek philosophy. You will find them in Scripture. They are knowable by human nature, which God designed, not Plato. Plato first formulated them, but he did for virtue only what Newton did for motion: he discovered and tabulated its own inherent foundational laws.

These four are called "cardinal" virtues from the Latin word for "hinge." All other virtues hinge on these four. That includes lesser Virtues, which are corollaries of these, and also greater virtues (the three "theological virtues"), which are the flower of these.

Courage may not be the greatest of virtues but it is the necessary one:

Courage is not simply one of the virtues, but the form of every virtue at the testing point, which means, at the point of highest reality.
— C.S. Lewis

Courage is the greatest of all the virtues. Because if you haven't courage, you may not have an opportunity to use any of the others.
— Samuel Johnson

Courage is the first of human qualities because it is the quality which guarantees all others.
— Winston Churchill