derived from Yiddish, a kadevil is a person, persons, or thing, that interferes in your life or cuts you off just as you are about to get something you are waiting for/ want.
The kadevil is oblivious to the role s/he plays in interfering with your life.
Just as you approach a line for a movie ticket booth, 8 kadevils swoop in and get in front of you at the last minute, forcing you to wait.
A salesperson is about to make a sale, and just as she is closing the deal, the kadevil phone rings, her intended buyer becomes distracted, and the buyer has time to reconsider and decide against the purchase.
12👍 3👎