Death Note

Yeah
If I get drunk enough I can't log into my computer despite having the password firmly in muscle memory, so I reckon if I really pushed my limits I could do it with my name too

Takooey shibemaaroo

I don't know why it would be your legal name if nicknames don't work.
I mean a good nickname implies that's what people actually call you, but changing your name legally just means that's what the government calls you

nice speedwatch/read. in the universe of death note, all humans go to purgatory/mu/nothingness when they die. whether they use the death note or not doesn't matter. this is why light has that small conversation with ryuk at the end. it's just there to scare the user, basically.
and using the deathnote doesn't do anything to you, getting shinigami eyes cuts your lifespan in half. i don't think it's mentioned that people who use the DN die in miserable ways either, and as mentioned previously, all humans go to purgatory when they die.

Additionally it doesn't say it has to be done in the same session. May as well try it once every few days with Watashi stopping you and eventually you'll get it wrong 4 times.

How many times would someone realistically misspell someone's name if their intent was to kill.

>Get deathnote
>Put your own name in: user dies painlessly in his sleep, pleasantly drunk and surrounded by beautiful women who love him on a random day after the start of year 100,000AD (or whenever humanity collapses)
How could you lose?

It's pretty vague, but the names you see with the shinigami eyes of death are the names needed to kill that person. You will see the names even if that person isn't registered in the family registration. For example L's true name is canonically L Lawliet, however he had no birth name, and L was just a nickname given by Watari. So it seems to be that whatever name you primarily went by would be your true name. This is supported by Beyond Birthday and some others.

Imagine buying this and having the Spanish under it.

Now imagine trying to kill the Phantom Troupe members with that rule, and fail.