10 Video Game Heroes That Got Everyone Killed
4. Commander Shepard - Mass Effect 3
Mass Effect 3's "Destroy" ending - typically the one accepted to be canon - involves Commander Shepard destroying the mass relays, the ancient machines which facilitate faster-than-light travel.
And by destroying the relays, Shepard ensures that the alien races fighting the Reapers in Sol - that's Earth's solar system - are now effectively stranded there.
It goes without saying that the many alien species stuck on Earth wouldn't be much happy about that, especially those which require specific nutrients in order to survive.
Beyond that, most species wouldn't live long enough to make the arduous journey home using their own faster-than-light drives, nor have the fuel to get there in the first place.
Combine all this with the relative scarcity of resources on Earth and Shepard's destruction of the mass relays would almost certainly result in massive conflicts and death on and around Earth. Well done, Shep.