Good Verses showing the lake of fire which is the second death.......If Jesus didn't come and die or become a sin offering for mankind, all of mankind would have been put in the lake of fire, including, David, Solomon, Isaiah, Ezekiel, Noah, Abraham, Moses, Elijah, etc. Paul says in Romans 5:14 Nevertheless death reigned from Adam to Moses, even over them that had not sinned after the similitude of Adam's transgression, who is the figure of him that was to come. This is talking about the first and second death.
Now let's take a look at what Paul says in Hebrews 10: (v.26) For if we sin willfully after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins. Now do we understand what’s being said here? If you sin willfully after you have knowledge of what the truth is, no more animals are going to die for you. (v.27) But a certain fearful looking for of judgment and fiery indignation, which shall devour the adversaries. Now if you are being deceived into believing that once you are under God’s grace you no longer have to keep his commandments, all you have to look forward to is the day of judgement and the lake of fire (fiery indignation).