In an early episode of Babylon 5, the Centauri ambassador Londo Mollari explains to another character that Centauri often have dreams about their moment of death, and that once he came to the station and met the Narn ambassador G'Kar, he recognized him as the person who would, at one point, strangle him to death. In a later episode, we see a glimpse of the future, when Londo has become emperor. But it turns out that he's been infested by a parasite that can control him, except for when he's just drunk enough to put the parasite to sleep but still retain enough sense himself, and in this glimpse of the future we see him do a heroic thing. But in order to keep the parasite from finding out and stopping it once it is again awake, he calls on his loyal friend G'Kar to kill him before it wakes.
So, "Londo will be killed by G'Kar" is not a spoiler. But "Londo will be killed by G'Kar because that's the only way for Londo to save his former allies from the parasite infesting him" is.
