Good One, Babe
Very rare1.1%GrindOptionalAnywhere
DLC2: Guns, Love & Tentacles
Watched Deathtrap kill 50 enemies.
Deathtrap appears on three separate occassions during the DLC. Just stand back and let him kill. you can weaken enemies `- but deathtrap must land the killing shot.
If you miss this, go back to Xenocardiac Containment and redo the Empowered Grawn boss battle - Deathtrap will be there for that...
Also, progress is profile-wide (not per character) so you can continue with fresh character if you want.