Difference between 闇 (yami) and 怨 (on)


In two anime series, HUNTER×HUNTER and D.Gray-man, the word 怨【おん】 was
translated in the English subtitles as "darkness".

闇【やみ】 is another word for "darkness". What is the difference between these two
words?




闇{やみ} and 怨{おん} are not really related at all.

  * 闇{やみ} means "darkness", approximately (as well as some related concepts).

  * 怨{おん} doesn't stand on its own, but is part of words like 怨{うら}み and 怨念{おんねん} which both mean "grudge", approximately.

Maybe if you explain what made you think they were related a better answer can
be given?

