Mosiah 17:16 - 17:20

Mosiah 17:16 And it will come to pass that ye shall be afflicted with all manner of diseases because of your iniquities.

But there will be repercussions against the king and the priests. They will afflicted with various diseases because of their sins.
[Could be sexually transmitted diseases, etc]

Mosiah 17:17 Yea, and ye shall be smitten on every hand, and shall be driven and scattered to and fro, even as a wild flock is driven by wild and ferocious beasts.

They will then find themselves hunted like wild animals and have to flee to stay alive.

Mosiah 17:18 And in that day ye shall be hunted, and ye shall be taken by the hand of your enemies, and then ye shall suffer, as I suffer, the pains of death by fire.

Eventually they will be caught and burned at the stake just like Abinadi was.

Mosiah 17:19 Thus God executeth vengeance upon those that destroy his people. O God, receive my soul.

God will make sure that those who kill the prophets and the righteous pay for their crimes. Abinadi now dies.

Mosiah 17:20 And now, when Abinadi had said these words, he fell, having suffered death by fire; yea, having been put to death because he would not deny the commandments of God, having sealed the truth of his words by his death.

Abinadi is now dead because he would not deny his testimony of Christ nor quit telling the people about their wickedness and of the wickedness of their leaders. He put a seal of validity by being willing to die a very painful death to back up his words.