ひどく暗かったので、彼らはほとんど見えなかった。

It was so dark that they could hardly see.

ひどく暗(くら)かったので、彼(かれ)らはほとんど見(み)えなかった。

Hidoku kurakatta node, karera wa hotondo mienakatta.

酷く (ひどく)

very much; terribly; badly; awfully; extremely

暗い (くらい)

dark; gloomy; dark (in colour); dull; depressed; dispirited; sorrowful; bitter (as in a dark past); unclear; unfamiliar; unknown

ので (ので、んで)

that being the case; because of ...; the reason is ....; given that...

彼ら (かれら)

they (usually male); them

は (は)

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

殆ど (ほとんど)

mostly; nearly; practically; well-nigh; almost invariably; all but; just about; almost

見える (まみえる)

to have an audience; to meet; to see; to face (an enemy); to confront; to serve (esp. as one's wife)

Readings: アン、くら.い、くら.む、くれ.る

Meanings: darkness, disappear, shade, informal, grow dark, be blinded

Readings: ヒ、かれ、かの、か.の

Meanings: he, that, the

Readings: ケン、み.る、み.える、み.せる

Meanings: see, hopes, chances, idea, opinion, look at, visible