Wiktionary
troublingly
adv. In a trouble#Verb manner; causing one to be troubled
Usage examples of "troublingly".
The thing that had crashed down on the wall sawteeth was a thin, snow-white cylinder that looked troublingly familiar until Floyt placed it: a flagpole just like the one in their own garden, only its red, white, and blue flag displayed a coiled-rattlesnake emblem.