Dead Effect 2

its on mission 4 Crystals of Power, best weapon choice is to use a Combat Bow (Like Epirus-Tab 10) and increase its Damage, keep in mind about Bullet Time as it will be ur best friend. Play on Easy for 1 shot kill Potential. Two different enemies u will be faced, For Zombies keep distance and try not to miss since it has chance to miss from afar (and most annoying) barrel roll, this is where Bullet Time will be ur friend and for Soldier & Boss stay as close as possible

This is not too bad and personally would not recommend to do this alongside the secondary weapon achievement. Have a fully upgraded assault rifle/weapon and on easy difficulty. A lot of the enemies are bunched up so any missed shots will generally hit the enemies behind the one you are shooting.

The delta soldiers move around quite a bit so shoot when you know you will get a hit. After hacking the terminal a boss will spawn down a ramp. You can easily take him down with upgraded stuff. Bullet time is also a good thing to use.

After defeating him and picking up the crystal you can sprint past all the enemies to the end of the level to ensure you are under 10 minutes.