I had very similar with my sister 10 years ago. I tried so many things but stumbled on two words that changed everything. These two words really helped. My sister often would complain and then rant and rave.

I would listen to her until it got the point that more discussion would not help. I would then say "dead horse" and she would then continue and I would say "dead horse". Early one she might make me say "dead horse" 10 times before she knew that I ad heard her point but would not listen any more.

It rarely takes more than one "dead horse" to steer the conversation.

OP, this is your sister. Say what you would say to a friend.

"Larla, you seem really down lately. I find it hard to listen to your negativity when we discuss things. Have you tried talking to a therapist?"

Reading your first post, and calling your sister stubborn, confrontational, and opinionated, and I wonder if you should just cut back on the amount of time you spend with her.

I would:
control the amount of time you spend with her
tell her when she starts ranting that you don't want to discuss it anymore (if it isn't productive)
suggest she get help for the other problems in her life.

OP here. I didn't exactly hang up on her. I said "gotta go" and then hung up. 7:56 asked why is she like this? She is simply a big complainer and LOTS of drama (it's gotten worse over the years). She thinks her problems are bigger, she works harder than other employees and in general, her life is more difficult than anyone else's. If she were s friend, I would have no tolerance for this.

If my sister hung up on me, I would probably wait for her to call and apologize. I would be pissed!

You hung up on her, so you need to apologize.
Why is she like that? Is something making her unhappy? Can you cut her short and change the subject when she starts a tirade? Some people are just negative and complaining. Is there anything that is easy to talk with her about? Do you have any interests in common? Try to expect less from her, learn to tune out her Debbie Downer ways, and if you need to reduce the amount of interaction you have with her, reduce it.

I cut my sister off about 6-7 years ago because I was tired of all the BS and other nonsense. I just don't have the patience or desire to deal with it so I'm probably not the best person to give advice.

I have never been close with my sister and we used to fight terribly. Once I recognized that I will never be close to her and I don't trust her but wanted to keep the peace things improved. I tend to keep things pretty smooth and even when dealing with her and just apologize right away if need to (she has never apologized to me or acknowledged when I apologize to her) I don't have expectations that our relationship will be good, I don't have expectations that she will even be nice and kind. It totally sucks and I wish I had a close sister relationship like I see so many others have but it's not what I will ever have.
I think it is OK that you gave it a few weeks but ultimately you hung up on her so you owe her the apology. Since it has been so long I would probably let the apology go but maybe text her something funny or random. I find with my sister that is the easiest way to ease back into talking again when we have a period where we don't speak.

I know the feeling, OP. No advice, just commiseration. I do the right thing and keep in touch because I want to and because I know it's right. I know my sibling will never appreciate my efforts.

I have had ongoing differences with my sister-nothing major, simply we are different people. She is stubborn, confrontational,and opinionated. As long as it doesn't involve me, I tend to stay out of her rants. Honestly, I don't think she is well liked at work, but I think it's because she is sometimes miserable to be around. She's the kind of person who can be in a "mood". Anyway we recently, we had a phone conversation that I did not agree with her. It's really quite silly--we both were invited to a party. I planned to attend, she did not and proceeded to rant and rave about why she was not going. BTW, the invite had come thru me and I was the one who had to tell the hostess that she was "busy". In the middle of our conversation, I expressed that I thought she was being mean-spirited and abruptly ended the conversation (like I hung up). Fast forward 3 weeks later, I have not heard from her. It is clear to me that if I don't make the first move, we will be like those siblings who don't speak for 30 years. I am not a stubborn person, but I am tired of her attitude. WWYD?