"he seriously told them and begged them." Here the words "testified" and "urged" share similar meanings and emphasize that Peter urged them strongly to respond to what he was saying. Alternate translation: "he strongly urged them" (See: [[rc://en/ta/man/translate/figs-doublet]])
The implication is that God will punish "this wicked generation." Alternate translation: "Save yourselves from the punishment that these wicked people will suffer" (See: [[rc://en/ta/man/translate/figs-explicit]])