Damn, I'm Good
Complete the SP campaign on Insane Difficulty
Again, just as it says. While the game can be tough in spots on Easy, you have your work cut out for you on Insane.
Kill 10 aliens with environmental explosives
For this one you need to kill 10 aliens with explosive items that are found throughout the games environments.You can blow up cars, barrels and propane tanks to get the job done.The best way I found was to grab propane tanks and throw them at groups of enemies to get the job done much quicker.
Downtown Barrel Beatdown
Kill 10 aliens with tossed objects
You can use the same technique as Dead Useful by tossing propane tanks to kill enemies, but you can also use anything else for this achievement.Anything that can be picked up and thrown will kill an enemy, although it may take more than one throw to finish them off for good.
Doodle something on the whiteboard in SP
Immediately after the game starts, you will come to a locker room and an EDF soldier will be standing beside a whiteboard. Use it to draw something – you know you're going to draw a penis- and when you step back the achievement/trophy will pop.
Duke Angry, Duke Smash!
Kill 15 aliens with melee attacks while on steroids
When Duke pops his steroid pills, he goes into a rage mode a la DOOM’s berserk mode and one hit kills anything with his fists.The first time you get the pills is during The Duke Cave, and they pop up after you replace all three power cells. Once you grab the pills, a load of aliens enter the room. Take the pills and you should be able to kill 7 or 8 of them before it wears off.Simply reload the checkpoint which will place you right when the pills appear again and repeat until you get the achievement/trophy.
Kill 50 aliens
Easily acquired simply by playing through the campaign.
Get knocked down 10 times
There are few enemies that will be able to knock Duke down on his duff, but one such battle has it happen quite a lot. When fighting the Alien Queen, her purple shot that comes from her mouth will knock Duke down without killing him.Let the blast hit and then recover your ego and go for another blast.Repeat until the achievement/trophy pops.
Flagon of Chuckles
Drink a beer in SP
Beer is plentiful throughout the game. Simply grab a cold one and crack it open and enjoy the good times.
Fork the Pork
Kill 6 aliens with the forklift
When you first enter the Forkstop part 2, there will be a forklift on the right.Lower it and take it for a spin.While driving through the hallways, some aliens will appear.Simply run over 6 of them for this reward.
Kill 15 frozen aliens
During the level The Shrunk Machine you will get to use the freeze ray for the first time and then enter a room full of enemies immediately after. Concentrate the freeze beam on the aliens until they are iced and then either shatter them with a melee attack or perform an execution on them. Do this 15 times and call it a day.
Carry the gold pistol through the whole SP campaign
You are given the gold pistol at the start of the game and to get this achievement/trophy, you need to keep it with you throughout the entire game.Be mindful when picking up new guns that you don’t have the pistol selected and watch that you aren’t standing over any weapons on the ground when reloading. If you managed to keep the gun with you the entire game, the achievement/trophy will pop as soon as the credits start rolling.