There is a foolproof method to get the hard badge. Ignore all powerups except the minesweeper powerup and the invincible powerup. Collect those and destroy the mines which will give you points. You get more points by ramming into the mines. Killing mines does not increase your size, which means that you can evade incoming mines easily. Keep this up and eventually you'll hit the 1938 mark.
Whew just got the hard badge. Here's some tips. For the collecting skulls missions, equip high health low strength parts. You don't want to kill the buildings too fast because they produce humans and you want to last longer so that you can collect more skulls. For those missions that require you to destroy everything, get Cyclops Eye (for anti air) and Caterpillar tracks (for fast movement). Also get power paws to destroy stuff faster. For mecha missions, get chicken wings for tornado or cyborg head for incinerator. Don't expect to outrun the mechas. For the very last mission, get polished horns for ram charge and spam power all you've got. Drive the mecha to a corner and use ram charge so you hit him twice with the rebound. Hope this will help.
IMO Cyclops Eye is the best upgrade. Its the 4th eye upgrade. It destroys any airplanes or helicopters anywhere on the map instantly without the need to aim. Then you can achieve the rest just by buying more power and getting caterpillar tracks (the last leg upgrade). You will eradicate everything on land at a very fast speed and the planes won't bother you at all.
Nice game, but the inability to restart instantly when you accidentally kill a civilian is kind of annoying even though it may seem like a small thing.
 "Bubbles 2"){kind=icon}
 "Ultimate Assassin 3"){kind=icon}
 "Villainous"){kind=icon}
 "Max Mesiria Chp2 RPG"){kind=icon}
 "Racing Comrade!"){kind=icon}
 "Maze Stopper 2"){kind=icon}
 "Days of Monsters"){kind=icon}
 "Flagstaff: Chapter Three"){kind=icon}
 "RPG Shooter: Starwish"){kind=icon}
 "Elements of Arkandia"){kind=icon}
 "Frontier"){kind=icon}
 "Castaway 2"){kind=icon}
 "Typing Ninja Hunter"){kind=icon}
 "Sieger: Level Pack"){kind=icon}
 "Vampire Physics"){kind=icon}