There are a total of 12 possible combinations of corebots and frames.
After unlocking all 3 corebots (Mack, Seth & Duncan) and all 4 frames (K-9, SP-DR, AP-3 & FL1-R), you want to go back to your crawler, and on the workbench to use core swap and make combinations of corebots and frames. After making two, back out, and go outside. Find a group of enemies and use the lethal attack of these combinations on an enemy group for it to count. Now back back to the crawler, and make a new combination, and repeat. You can keep track of your achievement progress via the achievement tracker.
All 12 possible combinations are as follows:
- Mack as K-9*
- Mack as SP-DR
- Mack as AP-3
- Mack as FL1-R
- Seth as K-9
- Seth as SP-DR*
- Seth as AP-3
- Seth as FL1-R
- Duncan as K-9
- Duncan as SP-DR
- Duncan as AP-3*
- Duncan as FL1-R
* - denotes default combination
You may want to set up a grid on excel or use this list to check off the combinations you've used.
You will also unlock Identity Crisis while doing this: