ReCore

As is previously mentioned by the other two guides; outside of Joule's Crawler in the Granite Steps are two sets of level 2-3 spider-bots. These enemies are perfect for this achievement and the Split Focus achievement.

Damage the enemies using the RT gunfire mode, while making sure your corebot isn't attacking them by continually spamming the X button to call them to your side.

Once they are weak enough, it'll take some luck and timing to get them lined up. Below is my Game DVR footage of when I got Chrom-tastic! (It's cringey but I hope it helps)! :)

Next to the base of Jolie has 3 blue enemies (Level 2/3) that are much better to make the achievement.

Climb up and down until the enemies are straight and shoot them

Have patience and good luck, map at the end of the video

I think this achievement is not easy, you really need to be patient.

1. There are two groups of enemies(LV2~3) near Joule's Crawler, a group of blue, another
group of red, choose "red group"
2. Use RT to weak the enemy(don't kill anyone, just Leave a little bit of energy), then hold RB to charge(Chrome Shot).
3. Have patience, make sure they are on the same trajectory(need a little lucky), then fire.

@ pantyhamster
I lured both groups (3 x blue and 3 x red) together when weakened, gave me plenty more options to get three in one shot with six of them.

**(In the process, keep to input X button, call your robot back, don't let it to kill the enemy)

**(If you input X button correctly(tap, tap, tap), your robot will have a sign(back / come here), it will not attack enemies.)

**(don't use robot T8-NK, FL1-R, sometimes you input X button too long, that will trigger the robot ability.)

This is the easiest method i have discovered, you can get the achievement in first try.

Right when you exit Joules crawler, there are 6 crawlers near by (3 Blue & 3 Red) . Get 5 of them together and shoot when at least 3 of them are aligned in a straight line. Always remember to keep spamming to keep your core bots from attacking the spiders. This method is far easier than trying only with 3 spiders. I got this in my first try.

I used the enemies at the end of well of shadows.

it spawns a set of 3 spiders multiple times, the spiders dont move much and if you lower their health just a lil bit

Spam x to prevent corebot from attacking.

Aim for the center with a bot on either side and you cant get it fairly easy.

the spiders stand staggered from each other and they rarely move, and when they do move they stay staggered, and the aoe is large enough to hit them all.