This is my first guide, so leave any advice.
Personally, I used a guitar peripheral to play this game (I found it was the easiest), but a normal controller and a drum kit are also options.
Completing all the badges on Thrasher will also unlock the achievements for the Hard and Normal difficulties.
This will take a certain amount of skill, so all I can offer is advice and some strategies that I utilized in order to complete this.
I would not suggest going for the Score,Combo,and Challenge badges until you have collected all the data crystals. It just makes it easier to have full powerups
NOTE: You do not have to complete all 5 badges in one attempt, you could get 1 badge per run through and do a level 5 times if you want.
Score Badge/Combo Badge: Each level has a score and combo that must be reached to unlock this badge. These are seperate badges, but the strategy for them is basically the same.
The shield will be your biggest help in keeping your combo alive, which equates to more points. When I found myself getting swarmed, I would pop the shield and ignore blast for the following reasons:
--Blast requires more energy
--Blast only increases your combo by 1
Then go through and kill those enemies with that shield up! If your shield is about to run out (with mutants still swarming) then it becomes a judgement call. You can use blast and wipe them all out, or spam the back button to make sure that shield activates asap. I usually opted for the shield option and would rarely get hit.
For the timed enemies, it is random which sequence you have to play sometimes it easy...sometimes its brutal. Some times a difficult one would break my combo, Luck did play a factor here, but a very minor one
Also, learn the levels. Figure out where the shield/blast is a must to conserve energy and where it is not needed.
Accuracy Badge: Each level has a target accuracy that must be reached, these are usually over 90%. For this, all I can say is don't miss notes, and don't overstrum.
Continue Badge: You must not use any continues to get this badge. This will probably unlock majority of the time without even trying. If you are dying, you can just spam notes and never die. Easier to spam with a Drum Kit.
Challenges Badge: A level can have anywhere from 1 to 10 challenges. From Rescue, Kill and Pick-up challenges.
If using a guitar, save Blast for challenges, most importantly the pick-up challenge because you literally get about 2 seconds to complete some of them.
A drum kit can be very helpful to complete some of the later challenges.
When you get to a challenge, spam the pedal and hit the Red/Yellow simultaneously with one stick and Blue/Green with the other. So your hitting all notes at once constantly. If you're doing this correctly, the mutants will die as soon as they spawn.
Edit - From ticonderoga360 "if you spam with the drum kit, it's much easier to use the ABXY buttons than spamming the pads with sticks. I was using a world tour kit so that's why I tried it".