Matriarch Benezia (enemy)

Matriarch Benezia is a very powerful asari biotic and spiritual leader among her people, but Shepard finds her working alongside Saren Arterius, leading to a deadly confrontation on Noveria.

Mass Effect
Deep within Noveria's Peak 15, you will encounter Matriarch Benezia in a secure lab. You can talk to her and get a few questions answered. If you have Liara in your party, there are some words exchanged between mother and daughter. Once you are done Benezia will place the whole squad in stasis while her commandos move into position. When you regain control you'll find yourself in the middle of what's arguably the most difficult battle in the game.

Tactics

 * While dealing with the commandos and geth that Benezia summons, move to the right side of the room so that you'll be out of Benezia's line of fire while dealing with three waves of enemies. Once all the enemies are down a cut scene and conversation will begin, after which you'll be point-blank with Benezia with several commandos coming in to assist her.
 * Immediately hit Benezia with Lift or Neural Shock - otherwise you'll get a faceful of biotics and gunfire. Hit her with everything you've got and above all don't let her stand up.
 * Hammerhead or Sledgehammer rounds in especially a shotgun can be particularly effective at keeping her off balance. Then you'll have the three Commandos to finish off, but you'll have done that before.
 * Alternately you can run like heck from Benezia and try to get some of the Commandos down first, but be aware that Benezia will start following you around, so it can turn into quite a chaotic chase through the corridor. It can work, but if you're ready to hit Benezia hard and fast the instant she finishes her speech you have better odds.