After the death & resurrection of the two witnesses (Rev. 11:1-17), v18 provides a summary of the final 3 1/2 yrs of the Tribulation.
1. The nations will show their utter hatred for God.
-Rather than repenting upon hearing the message of the two witnesses and observing their miracles, the vast majority of mankind will only grow harder towards God and prepare for the Battle of Armageddon. Read Joel 3:9-13
Rev. 11:18 "And the nations were angry,"
2. The Great Tribulation
-The last 3 1/2 years of the Tribulation will culminate with God pouring out His "Vials" of wrath upon those who follow the Beast.
"and thy wrath is come,"
3. The Judgments
-The saved shall be rewarded at their judgments while the lost will receive their final condemnation.
"and the time of the dead, that they should be judged, and that thou shouldest give reward unto thy servants the prophets, and to the saints, and them that fear thy name, small and great; and shouldest destroy them which destroy the earth."
LESSON - There are no second chances after death. This provides additional proof to the message given by Abraham to the "nameless" rich man in Lk. 16:31 that even miracles will not convince a "sin-hardened" people to repent. We must do our job to convince as many as will hear our message that God is love but "He shall have judgment without mercy" (James 2:13)