I liked the scene where the guy was completely cut in half with the chainsaw.
(completely) cut in half
cut in two
「I liked the scene where the guy was completely cut in half with the chainsaw.」の直訳は「人物がチェーンソーで真っ二つにされるシーンが好きだった」です。
「真っ二つ」は「cut in half」か「cut in two」です。「completely」をつければ「真っ」のように強調をつけます。