Simple:
* The old house had a sinister air about it, with its boarded-up windows and overgrown garden.
* Her smile was strangely sinister, making me uneasy.
Figurative:
* The news of the impending war cast a sinister shadow over the city.
* The politician's speech was filled with sinister undertones, hinting at violence and unrest.
Literary:
* The flickering candlelight danced on the walls, casting sinister shadows that stretched and twisted like phantoms.
* The villain's plan was as sinister as it was intricate, designed to bring about the downfall of the entire kingdom.
Specific examples:
* The detective felt a sinister chill run down his spine as he discovered the hidden message.
* The scientist's experiments, while groundbreaking, had a sinister edge, raising ethical concerns.
* There was a sinister gleam in the thief's eyes as he approached the unsuspecting victim.
Remember: "Sinister" implies something evil, threatening, or harmful. Use it carefully to convey the right meaning and tone.