I had an old keylogger I used for testing anti-virus/anti-keylogging software.

My sister was annoying me.

I now have her Facebook password.

Not necessarily a bad person, it would take a lot more then stealing a facebook password to be considered a "bad person" in my eyes. However it really depends on your overall ethical views on what you think is ok/not ok to do.

BUT

Depending on where you are from, you may have just broken the law and criminal charges could be placed if you are reported to the police.

yes you are bad person, no one that is a good person uses facebook or cares about facebook.

Oh my word, I definitely laughed at CreativeMFS

For me it depends on what your sister did to annoy you.

Only if you enter her Facebook and completely humiliate her. Not that you should.

thats up to you..

LOL! Frape, much. I wouldn't consider it a bad thing unless you actually used that password.

_Wazzak

What would have to be done with said password to make it bad, IYO? Snooping or actually changing things?

Why don't you answer your own question. Obviously you feel bad enough about it to ask other people. Why don't you develop your own moral compass and realize you don't feel comfortable with it, therefore it's wrong. Besides you stole her password, and we all know stealing is wrong.
Though bit torrenting stuff is a little hazy in the copyright laws.

Bad person, no.
Bad thing to do, yes.