discussion acts that cancel each other on the charts?

[tili33]

when one releases the other one will most likely flop...

[GentleEarthquake]

I can only think of when there's some kind of controversy between two artists and people side with one of them the most, kinda like the Joshua and Olivia situation

[FightDragonsWithMe]

Beyoncé cancelled out Britney 

[Meev]

Taylor and Katy

Katy and Gaga

Gaga and Christina

Avril and Alanis

Olivia and Billie