An easy way to do this is to load up the Old Factory District Night Defence Challenge. Set up the trap of your choice (I recommend the Pyro Geyser, which is the fire trap) in front of the two outer barriers. Just place them right next to the barriers and the OD will run straight at them. When the traps are destroyed, you can instantly replace them with a new one so keep an eye on your traps.
If you only have the traps kill the OD, you should get 4 badges in approximatly 1-2 games. Failing or dying during the challage doesn't matter, the badges will still count.
Please let me know if I left out anything in this solution, I appriecate all the support.