This can be easily completed in Chapters 3 & 4.
When you are attacked by the Pack in Chapter 3, dance around until you get them grouped, then shoot one with the Javelin Gun. Press RB, and it will emit electricity from the javelin shocking the others.
The other place is in Chapter 4, when you enter the Renunion Chapel through normal story progression. Wait for the Slasher to climb the rail, then hit him with the javelin. Immediately press RB, and you will shock the Swarm crawling all over the floor. This is where I got it.
Credit to PowerPyx for the video upload.
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