for the hard bade u need to beat campaign mode to unlock it. the starteg i used was basically start of in middle and kill as amny as possible first, then start goin around the corners so all the zombies come in middle, while ur running around, quickly turn towards the middle to get some zombies then continue running around, repeat until every zombie is dead, then go to middle again.
ppl r so confused when they say tht i have so and so fighters while the enemy force has so much more... but the thing i its perfectly even because it counts all the other enemy forces not just 1
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 "Undercover OPS"){kind=icon}
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