Before there was Zeno Clash, there was Breakdown.
One of Breakdown's endings is a huge cliffhanger that sets up a potentially epic sequel.
THAT WE NEVER GOT
[spoiler]After spending the entire game brawling it out with superhumanoid badasses. The game pulls a rather brilliant fake-out moment while fighting the final boss.
There's a huge buildup to fight the final boss, and when you finally do get to fight him, it becomes apparent that you cannot beat him, and he promptly kicks your ass. You have failed. And to top off this failure, the arena you fight the boss at gets hit a fucking nuclear missile (launched in desperation to kill these superhumans) and blows you all to fucking hell.
Except... the game continues. You managed to survive the nuclear explosion and wake up in the not-so-distant future. Many years have passed, and the blast failed to put a dent into the superhumans, who have overrun the entire planet. Crushing human civilization.
After you wake up, you see the ruined civilization for yourself. Everything is destroyed, nearly all humans are dead, and the tireless superhumans continue to kill more people every day. Luckily, you manage to power yourself up one last time, and with the aid of a helpful female companion - travel back in time to face the final boss again at the peak of your power.
To make a long story, slightly less long. You beat the final boss, and save the world.
However, saving the world created a seperate timeline. One for the world which was spared from the superhuman rampage, and the other which was still being crushed by the superhumans. Alex (your companion) starts being yanked back through time due to a pendulum effect, who will return to her ruined future timeline.
And the game gives you a choice to follow her. Having saved the timeline you came from, you can follow her back to the future to save her timeline as well. [/spoiler]
The sequel could've been epic. The first game was just an exercise in fighting a few superhumans at a time, plus fighting the lowest ranking superhuman T'lan "general". I can't help but imagine how awesome it would've been to fight a planet full of these freaks, with the most powerful T'lan leaders.