Jamieson, Fausset and Brown on 1 Peter 4:18

18. scarcely--Compare "so as by fire," 1Co 3:15; having to pass through trying chastisements, as David did for his sin. "The righteous" man has always more or less of trial, but the issue is certain, and the entrance into the kingdom abundant at last. The "scarcely" marks the severity of the ordeal, and the unlikelihood (in a mere human point of view) of the righteous sustaining it; but the righteousness of Christ and God's everlasting covenant make it all sure.

ungodly--having no regard for God; negative description.

sinner--loving sin; positive; the same man is at once God-forgetting and sin-loving.

appear--in judgment.