LEGO Batman

I got this one in the very first villain level of The Riddler's Revenge. Not too many enemies to worry about and you can, for the most part, bowl right through them. Pretty short level, too, once you get a handle on where you're going.

I followed EvoHero's solution and it worked to a tee.

I just want to add that if you're playing single-player, you will not be penalized for killing your AI partner. Playing as Clayface, for instance, I accidentally killed my AI partner (The Riddler) twice. I feared that this would prevent me from receiving the achievement, being as how to complete the mission, from time to time I assumed control of The Riddler.

As it turned out, there was no need to worry. When I controlled Clayface, I didn't die; when I controlled The Riddler, I didn't die. And thus the achievement still unlocked, even though I killed the Riddler twice when I wasn't controlling him.

In sum, don't worry if your AI partner dies, whether at your own hands or the hands of the enemy AI; just focus on keeping the character you control alive.

You can do this on the very first level of the Hero missions (in story mode no less!) Just run through the level quickly; don't stop to collect studs or minikits, etc. I got it first try, no problem. Although, you could be in some trouble when you get to Clayface, just make sure you have all of your hearts and take out any goons ASAP. Oh, and make sure you turn Off ALL of your Power Bricks.

IncrediBoy's solution is the same method that i used to get the achievement, for an even easier run i would recommend using a character such as the SWAT to kill the enemy goons from a distance and it works on clayface when he closes the gap. Using free play and using characters like poison ivy to skip obstacles and poison made it a lot easier

I got this in the very first level (You can Bank on Batman). all you have to do is destroy the goons quickly to make sure they don't hurt you.