User blog comment:Chaoswolf75/What's the hardest choice you've had to made throughout the series?/@comment-4707281-20120712133754

Mass Effect 1: Virmire, who to sacrifice. Only if you're not romancing one of them though.

Mass Effect 2: Zorya, sacrifice the workers or go after Vido. It would be harder if you couldn't get Zaeed's loyalty on both though.

Mass Effect 3: Would be Geth vs Quarians, but making peace between them isn't that hard if you imported a save. As it is, the ending choice. Eventually I settled with Control.