Final Level: The Shard
Why It Sucked: Everyone either dies or turns their coats, with only Faith and Kate left alive by the end. And for what? They don't even jam a wrench in Project Icarus. The only victory is Faith's destruction of the mayor's servers, which we're sure will be fixed as soon as they can get the Geek Squad down there.
How We Would End It: Even though you rescue Kate, you're both still on the run. This victory like there was still plenty left to do, with little accomplished. Not an ideal resolution.