The audience was speechless at the movie's extremely gruesome depictions of violence.
事故現場は凄絶なありさまだった。
The accident scene was a lurid sight.
Standard kanji spelling.
Rarely used kanji form.
Compound of 凄 (sei, 'uncanny, terrible') and 絶 (zetsu, 'extreme, surpass'). The exact historical derivation is uncertain, but the combination conveys an extreme degree of gruesomeness.