The Ascent

As the description says, you need to kill a robot with energy damage. The easiest is using energy weapons. You can tell by the details of a weapon in the loadout menu (or at a vendor) what type of damage it deals. There are 4 types, i.e. ballistic, digital, fire, and energy indicated by the icons from left to right. The last one, the bolt of lightning, should be highlighted as shown in the figure below.

List of energy weapons

While you can buy an energy weapon fairly early in the game, I would suggest waiting for a bit. During the 4th main mission, Empowerment, you will go back to deepStink and encounter enemy robots (i.e. not the NPC worker robots) who will regularly drop energy weapons. Pick one up, and consequently use it to kill another enemy robot to unlock the achievement.

As commenter slxttylilninja noted, you can also unlock this achievement with the augmentation Neutron Beam. I am not 100% sure but I think this is the only augmentation in the game that deals energy damage.

*Edit: Added an image showing the enemy robots. While this is the location I have unlocked this achievement, later in the game you'll encounter robotic enemies in many more place (e.g. dNexus).