You HAVE to complete ALL challenges IN ORDER to get all the unlocks, but one of the HARDEST IS THE SEVENTH ONE!? SERIOUSLY!? Pounce three enemies in a row with a Lurker, means, I have to get three people to agree to line up and get pounced or get lucky as hell because that's not likely with how weak lurkers are.
Like I mentioned in another topic. TimeGate studios destroyed this game, leaving Gearbox last minute to connect the dots and finish the levels so it would be allowed to be sold. Things like the challenges they ran out of time on and barely got put in the game, that's why they're screwy.
And Gearbox tried to delay it again but Sega would have sued them.
Games List: http://i.imgur.com/n5R72Cl.jpg PC Setup: http://i.imgur.com/fUPqE7N.jpg