The word John uses could be translated as unbelieving
and so prompts us to think of those who reject the gospel. The ESV has opted to translate the term as faithless,
a word that directs our thoughts to those Christians who lose courage in the face of great pressure (Jeremiah 3:8–10). The latter option is consistent with the call to “conquer” (Revelation 21:7). See also Joshua 1:6–7.
8 But as for the cowardly, the faithless, the detestable, as for murderers, the sexually immoral, sorcerers, idolaters, and all liars, their portion will be in the lake that burns with fire and sulfur, which is the second death.”