It was such a shocking turn of events that I could have never imagined happening.
この場合、次のような言い方ができますよ。
ーIt was such a shocking turn of events that I could have never imagined happening.
「想像もしていなかった衝撃的な展開だった」
a shocking turn of events で「衝撃的な展開」と言えます。
ご参考まで！
The story was a horrifying outcome that I would not have even imagined
The story was a horrifying outcome that I would not have even thought of
The story had a series of horrifying events that I would not have even imagined
想像もしてない恐ろしい展開だった と言いたい場合は
「The story was a horrifying outcome that I would not have even imagined」
もしくは
「The story was a horrifying outcome that I would not have even thought of」
「The story had a series of horrifying events that I would not have even imagined 」
It was a terrible development that I couldn't imagine だと
Terribleは最低という意味です
Developmentはこの文章だと開発という意味です
英会話なんてuKnow? へお問い合わせして頂きありがとうございます。
またのご利用をお待ちしております！
・It had a terrifying twist that I never imagined.
「想像もしてない恐ろしい展開（ひねり）だった」
twist は映画の衝撃的な展開を指す定番の言葉で、terrifying（恐ろしい）と組み合わせることで「想像を超える恐ろしさ」を表現できます。
・It took a dark and unexpected turn.
「暗く恐ろしく、思いがけない展開になった＝想像もしてない恐ろしい展開だった」
カナダ 
アメリカ合衆国 
