Janna question

Against a janna it depends when she ults.

If you shunpo onto her and she ults, then you're left with no way to get back.

So you either have to,

shunpo onto a dagger thats already on her. That way when she ults you away, you can shunpo back.

or

If you can't get a q to be on her feet already, then you gotta shunpo onto her, w, and hope that she doesn't ult you back before you can get the reset from shunpo.

If she pushes you away and you can't shunpo onto her, then she's gonna outrun you no questions asked if you're just chasing her.

In a teamfight, if she's protecting someone, then its the same deal. Although getting her to ult, then going back to your team and waiting for cooldowns would be good too. Kinda depends on alot of stuff. Sometimes its just better to kill the janna over whoever she's protecting. Depends on how strong the target she's protecting is, how strong/tanky you are, and how squishy janna is.