The Atlus, Banshee, Phantom and Brute can all kill you in one hit if you are close, even at full shields and health. I have not observed such a from the Geth. Can the Pyro or Prime or any other unit kill you in melee with a single attack?
The Geth do not have a unit that can insta kill. However, this is balanced by the multiple units that have high burst damage.
- Geth Rocket Trooper
- Geth Hunter
- Geth Pyro
Also, the banshee's melee animation is quite long and can be interrupted if a biotic explosion is triggered before the impale occurs or if you had a missile launcher ready to take her out (the animation to bring out the missile launcher and to fire takes too long for you to save the party member).