The Boruto manga series might have already revealed how Kaguya managed to defeat a villain as powerful as Isshiki in the past ...

All Masashi Kishimoto needs to do for Kakashi is give him Purple Lightning Armor and he'll make a great comeback as a ...

This is because, due to the link, Boruto might have enough chakra reserves to keep his Karma in check, essentially eliminating the one weakness that could hold him down during a battle.