if you hated someone would you tell them?

yes

Depends on what it was I hated about them. If it was something said or done to me personally, then yes I would tell them in the hope of rectifying the situation. Otherwise I would usually avoid them, negative people is something we can all do without.

Of course, I'll even write it on a huge paper with blood and mail it to them just to get my point through

No I'd show them 😉

If they were not my boss why not? Make a slam book about them and let them have it.

only if they wouldn't gtfaway from me tbfh

No, I just wish them the worst in life