Aia begins powerless, which means that you will die quickly in the first rounds. However, the more you progress, much powerful she becomes. In the later stages, here's how to score enough (or survive):

• For the first 10-15 seconds, it's better to deflect bullets than try to fire once you have a gun.
  
• You can also grab quickly the red bullet gun and fire it between deflecting.
  
• When you unlock the double strike, you can fire your gun more than deflection. However, still,
  keep an eye on enemies. The more tainted the ground becomes, the less visible bullets become.
  
• Once you have the fire bullet gun, you're nearly invincible with double then triple strike. Yet, stay
  always alert, your blade can save you sometimes.
  
• If you can grab the green slice gun, it's even better, generally, when you arrive at that stade, you
  should be able to score enough or survive.
  
• It's possible that at the beginning of the round, you loose three respawns. Either you didn't
  deflect correctly or you tried to grab a gun and your attention was on the gun and not around.
  
• I found flirting with the arena limits working better for me than being in the middle of the arena.
  
• Don't stay in the same place, you can be quickly overwhelmed.

Some players find Wook easy to level up, others, including me, have an hard time with him, partly because he has no brainclap. However, the special attack is quite powerful but you need to master it if you want to survive.

• I found easier to stay where Wook spawn and use the special attack while turning on myself.
  
• Once you begin to move, you can overwhelmed by the enemies with the best guns.
  
• I only move if there is a real danger to be hit.

Wanderer has an advantage: you just need to keep your finger on the left click to fire. I never tried to use the tentacles with right click.

• When you can, grab the three bullets gun so that you have an advantage really fast.
  
• When it's possible, grab the red bullet gun, then the fire bullet gun. But don't try to grab them at
  the cost of a respawn.
  
• In the early stages, it's better to move around else you'll found yourself into a tornado of bullets.
  
• During these stages, pay really attention to the shielded enemies, they can sandwich you pretty
  quickly, so don't rush into them but try to make a path out of their reach until they loose the
  shield.
  
• When you arrive towards the 80%, it's better to move to find a more powerful gun, however, I
  tended to stay in the same area, as now, the tentacles and brainclap were more powerful and
  triggered faster, meaning that nearly every bullet thrown at me were destroyed. I was firing in a
  circle nearly everytime.
  
• As for Aia, the more tainted the ground becomes, the less visible bullets become. So pay still
  attention.

Q can become hard to master once you've passed the 60%.

• At first, follow the bullets you've slipped, to make sure they kill enemies.
  
• When the melter triggers, turn around several times to kill enemies as much as possible.
  
• When you're above 60%, don't move anymore. Stay in the center and deflect bullets in a regular
  and fast beat. Move only when you're nearly done to increase the number of enemies killed.

Gunner is quite easy to play though the fact he can't deflect anything can be annoying at the end.

• You can stay where you spawn or move back and forth. I largerly prefer the latter to score.
  
• You should let the flying gun shoot in the same direction as your gun at first. Once you see more
  enemies coming from behind, switch to protect your back. It's up to you, because I can switch
  nearly after 10-15 seconds as after 30-40 seconds. It depends of my respawns left.

The problem with Psyker is that you can be hit quickly, like Aia. However, she's not powerless at first.

• Don't use too much your blade, it's less effective than Aia's. Use it only if you're surrounded by
  bullets.
  
• At first, you need to avoid as much as possible to be hit, so fire at will.
  
• Wait at first where you spawn until enemies are coming at you, at least after passing the 60%.
  You can shoot, move to avoid bullets, but use the manastrike to clear a road and to grab a better
  gun. The higher you're close to 100%, the quicker the manastrike will be triggered. After that, it's
  just a question of directing the manastrike where enemies are the most dangerous (or towards a
  swarm).

I just want to say that UBERMOSH Vol.7 is a very hard game. If you don't achieve it using these tips, don't throw trash at me, it's purely your own skill issue. Also, thank you for reading!

All the credits goes to @vicrabb on neoseeker[neoseeker.com]
Here is the URL to the original guide made by them: URL to Achievements Tips[www.neoseeker.com]

All community awards and ratings are highly appreciated!
Happy Gaming!