Complex sentence: In the season ten episode "Luthor", Clark unintentionally visits a parallel universe where Lionel found and adopted Clark (Welling), who Lionel raised as a murderer who eventually kills Lex.
Split into simpler sentences: In the season ten episode "Luthor", Clark unintentionally visits a parallel universe where Lionel found and adopted Clark. Lionel raises his reality's Clark (Welling) to be a murderer who eventually kills Lex.