en_tn_condensed/2pe/02/04.md

did not spare

"did not refrain from punishing" or "punished"

but delivered them into hell

"but threw them down into hell" or "but sent them to hell"

to be kept in chains of darkness

Possible meanings are 1) "in chains in a very dark place" or 2) "in darkness that imprisons them like chains." Alternate translation: "where he keeps them in chains of darkness”