A little tough one between FF6 and FF7, but after a bit of thinking, I've come to a decision that FF7 is absolutely the darkest Final Fantasy game in the series so far. Reasons:

*CONTAINS FF7 SPOILERS!!!*



- The poor and oppressed people of Midgar
- Terrorist acts, AVALANCHE's dilemma about whether good intentions justify the acts
- Sector 7 Plate falling
- A powerful alien escapes a lab, scares the hell out of everyone and leaves behind nothing but a huge trail of blood and the company's president dead on his desk with a sword impaled through his back
- All those shocking things caused by Sephiroth/Jenova, like Midgar Zolom being totally slaughtered, appearance in the Shinra ship, (SPOILER)killing Aeris, burning up Nibelheim, messing up the main character's head, hurting everyone both physically and mentally and lots of other things