Beat Level 9 / Metropolis on Serious without dying.
It says without loading because you have to load when you die so this prevents people from loading just before they are dead. If you do die just restart the level from the beginning.
Below is a video trick that will allow you to get outside the level (for those who can't view the video all you have to do is rocket jump over the wall at the very beginning of the level and follow the edge of the map to the end and then jump on the last booster to get back in)
When you get back in near the end you will be in large area and will be attacked by multiple sets of enemies each activated when you pick up the items in the centre.
> Headless Kamikaze - Camp and use the Tommy gun / Laser.
> Harpies - Strafe and use the Laser.
> Werebulls - Jump strafe out of their path and use the the Double Barrel (or the Cannon or Rocket from afar).
> Kleer - Laser them while strafing their attacks.
> Biomechanoid Major (Red) - Strafe and Rocket or Cannon them
This will be hard so here are some tips:
1. Press Y on the difficulty select screen activate infinite ammo! (it doesn't affect achievements)
2. Strafe & Jump A LOT this will help you to dodge the many projectiles that will be flying your way!
3. Save rockets and other large weapons for the bigger baddies.
4. Press B and review the enemies and what tips the game has to offer on them.
Hope this helps!