I thought they beat Black Zetsu?

[Solo]

I seriously thought that dude was defeated. Was he not?

 

[Xāvî1]

Well that guy was Madys will who knew he would be so strong

 

[Megatolium]

Zetsu's have the ability to split bodies or perform mitosis remember?

 

[KGB Kakuzu]

You forget that unlike the rest of the Narutoverse, Zetsu is a real Shinobi who uses stealth.



Kuro Zetsu was bisected by Chojiro, but he wasn't killed. Last we saw he couldn't move his body. However, that entirely depended on Chojiro. Furthermore, it easily could have been a clone itself.



End of the day: Zetsu is a freaking Ninja! You don't defeat ninjas...they were never there to begin with

 

[VongolaX]

Who knew that the trump card was this.....

Regardless, the weak sh*t had to control a dying obito.