Trouble Beyond the Borders
A monoblade is a blade with an edge about a molecule wide and a low friction surface. The blade is usually quite thin and yet still heavy.
The extremely thin edge allows the blade to start to cut armor, the low friction thin surface allows the blade to pass through the target easier, and the extra mass increases the momentum of the blade allowing the wielder to use more of their strength.
It is expensive, but not prohibitively so.