Albedo has the highest defense

In the Great Underground Tomb of Nazarick, there were four NPCs who were exponents of melee combat. Cocytus had the strongest attack power when using a weapon, Albedo had an impregnable defense when in her heavy armor, while Sebas in his true form was stronger than either of them in melee combat. And then was one more, who was superior to all of them.
There could be no other reason for the Guardians’ surprise. Sebas, who could sweep away anyone before him in hand-to-hand combat, had been assigned to the simple task of reconnaissance. They could tell how seriously Momonga was taking this strange occurrence, and everyone was on their guard as a result.

- Overlord; Vol 1; Chapter 2