Story-related achievement.
*** Spoiler - click to reveal ***After the mission when you've to protect your boat while it attempts to leave Sunset City, you were informed that your friends are in trouble with Fizzco. You'd need to go to the locations of the troopers and the oxfords to rescue them from impending Fizzco bot attacks.
The mission is basically a horde mode scenario in which you take out several waves and variants of Fizzco bots. Bring weapons with electrical amps, and you should be fine. After you take out the Fizzco bots at the museum, go to the oxfords to repeat the process of killing more bots.
There are plenty of electrical barrels scattered all over the place during the battles. Use them to stun the bots if need be. Health and ammo boxes are all over the place if you need replenishments.
Take note of the objectives - if it's to kill bomb bots, for example, killing blade bots will not reduce the "to-kill" count.
Prior to the oxfords fight, Sam will lay tesla traps at various locations. Definitely use them (jump onto the them) to make things much, much easier.
Upon killing everything at the oxfords, you'll get to fight a large mech type robot for the finale. The tesla traps work wonders on him. Amping the TNTeddy with an electrical amp, plus a liberal use of the tesla traps will take out the boss pretty quickly and easily.