About three years ago, during an Internet argument on Twitter with a right-wing individual who lives in the same nation as me, I told them to go "follow their leader". They responded with a pithy rebuttal, seemingly unaffected; however, I know that just because someone seems unaffected, it doesn't mean that's always the case. I can't find their account anymore, so I can't apologize directly.
The number of people in this nation who've committed suicide is less than a permille of our adult population, so rationally, I'm aware that the chance that what I said actually spurred them to kill themself is so vanishingly small as to be completely insignificant: however, I still feel horrified that I even played the odds to begin with and made comments like that so callously, and am planning to start up a monthly donation to a local mental health and suicide prevention organization once I can reliably afford to again. That way, I can make restitution by participating in making sure that person and others have mental health support so they don't have to feel like the unthinkable is the only way out; and maybe find closure within my own heart, too, if I deserve such a thing.
If there's a moral to the story, its this; when you tell someone to kill themself, the /best/ case scenario is that they brush it off, but it still haunts you years after the fact. If you feel the urge, swallow it down, take a deep breath, and move on; if not for their sake, then for yours. There's no point to it at all.