If you're asking about how to 'pronounce' the English word "sinister", it would be pronounced something like "shini-staah". In romanji, it would be spelled "shinisutaa".
If you're asking "How do you say "sinister" in Japanese?",
the answer would be "fukitsu na", or 不吉な. Also "magamagashii" (まがまがしい).
不吉
to
Kurikku
Steevann
Nabigeetaa.
saigo
yoru
"Omosa."
meron
maikaru
kore
kaze