All 4 Uses

sinister
in
I Am Number Four
(Edited)

Or do I want something darker, more sinister, like the ability to kill without touching?
p. 121.1 *

sinister = evil, harmful, or frightening
A roar comes from outside, loud, animal-like, a sinister roar unlike anything I have ever heard before, followed by the sound of the metallic clicks of a gate being unlocked, lowered, and opened.
p. 383.2
They were different on Lorien, not quite as sinister looking.
p. 392.1
And then we hear a roar, not quite as sinister as the others, but loud enough so that we know it can only mean one thing: another beast.
p. 416.7

Definitions:

(1) (sinister)
evil or harmful; or making an evil or frightening impression
(2) (meaning too rare to warrant focus)
Much more rarely and only in very old usage, sinister can refer to the left side of something.