It started out hard... It's very unforgiving if you pick all the wrong perks. Ramp up your health and focus regen, especially the one that gives extra focus when you kill during bullettime; that one is ridiculous. Get all the gadget improvement upgrades; I regret not picking up 00 and struggling horribly during last stage. If you, like me, messed up your upgrades and active reloads, use your maxed Kaiser to clear Agent mobs; just turn on bullettime and get in range to fire one at a place where they're clustered. Boomstick does a good job of raping single agents as well; I suggest you switch over to that during the agent spam since missing the active reload for it is still acceptable and it has ample damage output anyway.
I cannot stress how important the Critter and Active Reload are. GET THEM. GET THEM FAST.
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