Black Widow: Recharged

There's a really good chance this will unlock naturally, if not in Arcade, then definitely in Challenge Mode. Challenge #6 "Mass Extermination" is a really good place to get this. In this challenge, you need to kill 45 Hornets, but before you get even remotely close to 45, the screen will be filled with Mosquitoes, Hornets, Grenade Bugs, and Thunderbugs. You need to kill 20 bugs without letting more than about .5 second to pass between each kill. If you shoot the Grenade bugs, any enemies they kill in their explosion will also count towards this, making this even easier to get. Once you've killed your 20th enemy within about 10 seconds, the trophy will unlock. 

This trophy does unlock in the video provided under After All , so if you need a visual reference, please watch Challenge 6 in that video.