What happens if no beings choose to act on one's bad karma?
You can find the answer for your question from a Jataka called &quot;Matakabhatta-Jātaka&quot;. Herewith I've quoted the section of the Jātaka which may answer your question.

&quot;In times past, brahman,&quot; the goat began, &quot;I was a brahman who taught the Vedas like you. I, too, sacrificed a goat as an offering for a Feast for the Dead. Because of killing that single goat, I have had my head cut off 499 times. I laughed aloud when I realized that this is my last birth as an animal to be sacrificed. Today I will be freed from my misery. On the other hand, I cried when I realized that, because of killing me, you, too, may be doomed to lose your head five hundred times. It was out of pity for you that I cried.&quot;
&quot;Well, goat,&quot; said the brahman, &quot;in that case, I am not going to kill you.&quot;
&quot;Brahman!&quot; exclaimed the goat. &quot;Whether or not you kill me, I cannot escape death today.&quot;
&quot;Don't worry,&quot; the brahman assured the goat. &quot;I will guard you.&quot;
&quot;You don't understand,&quot; the goat told him. &quot;Your protection is weak. The force of my evil deed is very strong.&quot;
The brahman untied the goat and said to his students, &quot;Don't allow anyone to harm this goat.&quot; They obediently followed the animal to protect it.
After the goat was freed, it began to graze. It stretched out its neck to reach the leaves on a bush growing near the top of a large rock. At that very instant a lightning bolt hit the rock, breaking off a sharp piece of stone which flew through the air and neatly cut off the goat's head. A crowd of people gathered around the dead goat and began to talk excitedly about the amazing accident.

Quoted from: Matakabhatta-Jātaka (Jātaka, Khuddaka Nikaya, Sutta Pitaka, Tipitaka)
The subject of Kamma is very deep and hard to understand. Only a Tatagatha Samma Samubuddha can understand.
Note: This is how I understood. I may be wrong but not Dhamma.