Every now and then developers try to make a fun trophy/achievement that is different than the usual beat a stage and get a prize, but it goes horribly wrong in Borderlands 3. I have no doubt Gearbox intended for Good One, Babe to be something that either happened naturally or occurred on your second attempt at the DLC. However, most people are not looking to do the expansion twice, much less for a trophy/achievement, making them rather desperate to not miss this task. Given there are only three instances where you get Deathtrap, one at the start and the other two at the very end, it’s a rough road but thankfully it isn’t too bad.
For this Borderlands 3 trophy/achievement you need to do it before finishing the DLC or you must replay it or find a way to get to those missions. As a result, you want to allow Deathtrap to kill every enemy but even that likely won’t be enough. Thankfully, there are two ways to easily do this.
The second time you get Deathtrap is during the mission On The Mountain of Mayhem. This occurs towards the end and should give you like 15 or so enemies to kill. The best time to get the trophy is during the boss fight. There are endless enemies that spawn and even if there aren’t you can simply die and retry, which Deathtrap will target over the boss. This can take a while but you’re guaranteed as many kills as you want. Best of all, the beam attack is a one hit kill for peons.
For those who finished that mission or want a faster version of it, the following mission The Call of Gythian is your best bet. The reason this is not our first recommendation is due to the relatively high stakes. While Deathtrap can and will kill every enemy along the path, finishing the garden fight (it’s the one where the objective is over an area after two or three sections of Deathtrap fighting) will prevent you from progressing forward. The idea is to get there, maybe kill an enemy or two, back out and redo until it pops.
You can mitigate some of the risk by making a copy of your save or being extremely careful but it’s far simpler to do the first method.