Last ressort just mean something used when you have no choice left. It's more similar to how G4 was a last ressort for Luffy post-skip where he only firstly used it in dressrosa, with it being a mode lasting a long while but coming with drawback.
So there are few differences between Zoro and Kid/Law
- Zoro's Asura so far is only used for temporarily attacks when Kid/Law's awakening is a mode
- Advanced color of conqueror played a role in scarring Kaido, something Zoro can only subconsciously use yet
So Zoro can temporarily be claimed to be low top tier when he subconsciously use coc+Asura, but it's not something he mastered yet, hence why he is rated below. Kid / Law however can freely use their mode longer than Zoro to hang on with those levels of power
So there are few differences between Zoro and Kid/Law
- Zoro's Asura so far is only used for temporarily attacks when Kid/Law's awakening is a mode
- Advanced color of conqueror played a role in scarring Kaido, something Zoro can only subconsciously use yet
So Zoro can temporarily be claimed to be low top tier when he subconsciously use coc+Asura, but it's not something he mastered yet, hence why he is rated below. Kid / Law however can freely use their mode longer than Zoro to hang on with those levels of power