@lololulu19 I have shared passwords in most relationships I'm in. Since I am my own email and network services provider, I have access to do a lot of things before anything has ever happened in my one relationship, and for some things, I still share passwords with one of my ex's.
It all depends on the situation and setting though. I have nothing to hide from my that ex (whose personal email and his mother's email are on my system), and as for my current Daddy, I have nothing to hide from him either. He has access to it all, but to my understanding, doesn't generally use it as he trusts me implicitly.
The few relationships I've had where they've gone really sour and sideways, I've always been the one to commit those acts of fuckery, however that did not happen until after some serious shady fuckery had already been committed against me, such as my ex planning to not tell me he was leaving until all of the sudden, he moved out with my brother of all people, who he used to get drunk on many occasions, and took advantage of, immediately after leaving me with a $583 mechanic's bill to fix my transmission lines after he broke them because he used my car without my knowledge or permission to move out while I was at work, and hit something in a parking lot in the process. In that case, I may or may not have logged into his company issued email account, changed his password, and then sent his HR manager a letter of resignation from his work account, then signed up his work email for ALL the porn emails.
The ex I'm still friends with to this day is a different story as we just got sick of arguing with each other because we're just too different to be compatible on that level, so I moved back into my parents' basement for a while until I moved into the place I'm in now, and left him with the apartment, all of my kitchen stuff (until he could get his own), and all the bills associated with the place, and thus left me with little to no responsibility in anything anymore. While we can both be kind of catty when things go sideways, in our older age, neither one of us will do shady shit unless it's in retaliation for other shady shit.