Once you beat level 25, you may feel an urge to level to 60 in order to beat level 26, BUT FOR THE LOVE OF ALL THAT IS HOLY, FIGHT THAT URGE! Leveling in the last level was how I beat it on my first try. It refills your HP and adds 5 more. What makes it even easier is that they are all agents, so max out the Big Kaiser and just shoot blades where they stand. Eventually it will get to the point where you won't even have to dodge most of the bullets.
Awesome game 5/5
If you know the strategy, the survival badge is MUCH easier than the hard badge, especially if you are playing on a laptop
Just lose one glade in survival and defend the other glade ftw
 "REPLAYING :the game:"){kind=icon}
 "The Final Death Wish"){kind=icon}
 "Pel"){kind=icon}
 "Async Racing"){kind=icon}
 "Globetrotter XL"){kind=icon}
 "Great Game 1/5"){kind=icon}
 "Neverending Light"){kind=icon}
 "Super Crazy Guitar Maniac Deluxe 3"){kind=icon}
 "Mushroom Madness 2"){kind=icon}
 "Death Vegas"){kind=icon}
 "Vector Runner"){kind=icon}
 "Balloon in a Wasteland"){kind=icon}
 "Toss the Turtle"){kind=icon}
 "Shopping Cart Hero 2"){kind=icon}
 "Zilch"){kind=icon}
 "Tower of Greed"){kind=icon}
 "Dinowaurs"){kind=icon}
 "Super Energy Apocalypse : RECYCLED!"){kind=icon}