Macduff was harmed by her love bomb that scales way higher than her normally and would’ve killed her if Jade didn’t get in the way
Chion also used his biggest attack yet while he was fleeing
Nothing suggest they would win a 1v1 against Macduff
Edit: in fact Chion got
stomped in a 1v4 situation and couldn’t do shit to « save » Percy it’s even stated that without Percy they would’ve died
Percy could do something against Meland while Isolde got stomped even with the love boost
I think it’s more about landing a blow that would kill Macduff not just touching him
Here they didn’t
really seal him and not knowing how they did it is important they might’ve had to
Meliodas too can harm Arthur and parry Chaos attacks
Lance fought a very suppressed Chaos