Despite how underpowered I thought the phoenix was. I think she slightly outclasses both sidious and Yoda's on screen versions. That being said, Logan killed her with a simple stab and I see no reason why these two working together can not replicate this feat. I think it will require a sacrifice though. One of them will probably have to die to do so.
Ahhh that is true. I forgot that bit.Still, sidious and Yoda are both powerful and fast. And that last display of power in x3 isn't how she is going to start the fight. If sidious can distract her with lightning or whatnot then Yoda could possibly impale her.
Unless your saying she only died because she wanted to, then they have no chance at all and they get shredded no matter what they do. But that's just spite.
They could probably do all 3 but she was literally ripping beings apart atom by atom, so what ever they do will have to be done extremely quickly. Like, literally within a few second window. If they hesitate to long K think she would overpower them or simply mirror their attacks and they will be on the defensive. And once she gets on the offensive I don't see many characters being able to withstand it for long.perhaps Dr. Manhattan and Surfer.