Ultimate badass 10g
Kill 10 Alien warriors in a row, without taking damage.
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Love at first sight 5g
Have a facehugger attach itself to you.
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Express elevator to hell 5g
Start the game
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Gamer over man! Gamer over! 5g
Die
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EAT THIS 10g
Kill an Alien warrior with a shotgun and have the resulting acid hit a team mate
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You're dog meat pal 5g
Kill a team killer (online)
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Hudson, run a bypass 5g
Successfully hack a terminal
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She's just a piece of plastic 5g
Discover Newt's "doll"
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Did IQ's just drop sharply while I was away? 5g
Complete the game on easy difficulty
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Stop your grinnin' and drop your linen! 10g
Complete the game on normal difficulty
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Not bad for a human 20g
Complete the game on hard difficulty
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Anytime, anywhere 10g
Play 3 successive rounds with friends online
That's all I can think of right now. :|