Comment by Zak

"Edge retention" is mostly achieved through high abrasion resistance. Sharpening is removing material by abrasion until the edge has a small radius, so ease of sharpening is mostly achieved through low abrasion resistance.

Being soft or brittle can also make forming a sharp edge difficult, requiring very light pressure in the final phases of sharpening to remove or avoid creating a burr in the case of softness, and to avoid chipping in the case of brittleness.

Of course all of these properties are affected by the heat treatment, which is often more important to the performance of the knife than the composition of the steel.