First post, w00t! Allright so I don't have a complete walkthrough of P.O.D., but I do have some very useful tips that will help you get that pesky hard badge very easily.
First and most importantly, if you solely want the hard badge PLAY ON EASY MODE. You still get the badge if you complete the game on easy difficulty, so feel free to wimp out.
Always shoot the UFO things first, worry about squids last. Squids don't cause much damage unless they are in a large group. Point, shoot, win. It's pretty much that simple from this point on.
If you are discouraged because you have completed this before and the game froze when you were on the last boss, that bug has been removed. SO GO GET THAT BADGE
Well that's all my advice for this game right now, yell at me if you need something more!
I'm working on getting a video for you guys!