こなければ

if ... do not come, unless ... come

→ 来る

こ come + なけれ Negative conditional + ば Conditional (if/when)

auxiliary · conditional Rare #42,120

if ... do not come, unless ... come

JA: 彼がこなければ、会議を始めます。

EN: If he doesn't come, we'll start the meeting.

Conjugation of 来る

Conditional

It would have been better if you had never been born!

You must be back by Sunday at the latest.

I wish I'd never been born.

If I hadn't come back here...

— レベッカ (1940)