The aggressor modification to an LDA shield uses a series of frequency modulators to set up a waveform in the LDA field, creating areas of destructive resonance.
When an object hits the LDA, instead of being displaced back it is displaced in all directions as the shield vibrates, tearing the object apart on a molecular level. This can be used to do severe damage to a ship at very short range by ramming them.
This model of aggressor shield is the most sophisticated available, forming a very stable destructive field. This doesn't suffer from the distortions and overloads common to modified shields, so you can use it without worrying about taking damage. It is a larger, and more power hungry however, so it usually is mounted on larger ships.