Survive 5 minutes when the tower is almost complete.
Depending on your skill in tower-defence style games, this achievement is actually quite easy. The problem, is stopping at "Almost complete".
Load up the first tower on easy difficulty in Survivor. Pick your 2 elements you are the best with, personally I always used Earth and Wind, just make sure you can handle a large amount of humans with whatever technique you use!
Now you are meant to let the humans build the tower all the way to the top. There is a little temple that they build on top and from the point that they plant the foundations for the temple, they only need 3 more humans to win! Let them plant the first bit into the temple (It will have 4 little pillars) then from here, simply hold off for 5 minutes. I suggest going for this after finishing the Campaign, or at least after a bit of experience, as that way you'll know how to best use your skills ( not get run over by cursed jars and priests), and know to watch for their construction building that spawns them half-way (Which should always be quickly dealt with).
Just a note for wasting a little bit of time;
When playing Survivor, there are boat waves like in the Campaign (Once you get that far). When a boat wave is up next, the humans stop spawning. Once you have eliminated the final one, the "Press " option comes up. Try to pick up on the humans not spawning, as that way, you can let the last one take the minute journey all the way up before you cruelly end his hopeless life. I then let the option to press wait 5 seconds before I pressed it. This will grant you a bit of extra time to breath.