in my opinion, the harbor is the second hardest out of the 7 stages you get to play on easy mode. i mean, the level is piss easy, until you get to the top of the giant missile...then i tend to lose a good bit of lives.
the hardest, would be the city, mainly because i only played through it once.
also, to add. i can't beat level 2 on normal difficulty XD
*edit*
11/40 challenge mode challenges completed
i will not complete them all, these fuckers are HARD. but its not going to stop me from trying, only takes two seconds to retry a level after a death. bad guy blitz 3, why are you harder than 4, and 5? I WILL BEAT YOU EVENTUALLY!
*edit* defeated bad buy blitz 2, which nets me 12 challenges completed. which being a number divisible by 4(40 challenges, 10 unlocks, one unlock every 4 challenges), unlocks something, and that something is the character probotector (from the european version of contra 3 and several other contra games)
*edit* SWEET JESUS CANDY MAN LAZER SEMEN FLAKES! bad guy blitz ownt
13/40
ya see, the reason its hard. you know, in shattered soldier, and contra 3, the part where you are hanging on a bar, and flying dudes are flying all over picking you up? that part, they grab you, and you need to kill them before they lift you off the screen and kill you. well these flyers, they kill you on contact rather than grabbing you without killing you. and they come in at random, so if you don't shoot them, you will probly die. also, if you grapple at a wrong time, and a flyer comes in AFTER you do the grapple, you are pretty much fucked and died for something you couldn't forsee.
suprisingly, it took me 3 attempts today to complete, after the part with the flyers, you get a crush power up, and you can pretty easily blast through all of the random ground enemies to the end.
*edit* some of these challenges are addictingly fun
speed run 3, i beat it BARELY
as in, i was in mid jump on the platform i was suppose to jump on to win with 0 seconds left
here is a video of a guy completing it, damn fun challenge imo
15/40