interpretting お前を倒さずして、消滅などできん！

Question

enemy returns a while after being defeated by the mc

mc「ど、どうしてあなたが……！　この間滅したはずなのに……！？」

enemy「お前を倒さずして、消滅などできん！」

enemy charges....

i will "do it" without beating you, i can't extinguish you, makes no sense in context.

What is he trying to say?

thank you

Answer 1

お前を倒さずして、消滅などできん！
I can never vanish without/before defeating you!

• 未然形 + ずして is a literary way of saying "without ～ing". It's a literary version of ～ないで or ～ずに. See: 闘わずして勝つ vs. 闘わずに勝つ
• 消滅する is intransitive.