(けんあく) 険悪な関係:a dangerous relationship – that is to say, a relationship which has gotten really ugly or bad, verbal abuse, etc. And you’re not sure how much more you can take.
(ぶっそう) Dangerous – in the sense of violence. Usually used in one of two ways:Don’t go there, that neighborhood is dangerous. or, it’s a dangerous world nowadays. You wouldn’t say that a mean dog is 物騒.   $$$SITU
うさんくさい Shady. Like an email from a Nigerian arch-duke or some guy asking you to come to his cult meeting.   PPP
(きみわるい) Creepy – more like 気持ち悪い (きもい) than 怖い. Usually used about animals:Slugs or lizards. Although it is sometimes used about homeless crazy people. Not that I endorse that or think it’s rad. But the “usually animals” thing sets it apart from きもい、which has a much broader meaning.
ない(あぶない) The most common word for “dangerous.” Also means “look out,” as in, if you’re on the sidewalk and a bicycle is coming towards you, you’d tell your friend “abunai” rather than the more direct “get out of the way.”
(いじきたない) This is an odd one! This is an insult used on someone who is so penny-pinching that they don’t have self-respect. Like if their hot dog falls on the dirt, they’ll pick it up and eat it, rather than buy another. Or if they lick the bowl clean because dammed if they didn’t pay for every molecule of soup. This isn’t stingy in the western sense of short-changing other people, refusing to tip, etc. Usually used like this:意地汚い人間.