If you use a 1 Hit-KO move on a pokemon holding a focus sash, does it KO or hold on using the sash?

Question

Curiousity

Answer 1

it will hold because of the effects of the sash, so if you use a 1 hit-ko use another attack so it will faint

but remember do not always rely on 1 hit-ko moves

Answer 2

The pokemon will hold on with 1 hp