The phrase "alarming feature" is correct and usable in written English.
It can be used to describe a characteristic or aspect of something that causes concern or worry.
Example: "The alarming feature of the report was the significant increase in pollution levels over the past year."
Alternatives: "worrying aspect" or "concerning element".
The most alarming feature of this election – so far – is the lack of public interest.
In spite of such measures, however, the most alarming feature of the Swedish economic crisis was rising unemployment.
Buried deep in this rather alarming feature in the Independent is the horrifying nugget that a bad boss can be bad for your heart.
The WHO report noted that the exposure of health care workers to the virus is an "alarming feature of this outbreak".
Readers React Mr. Goyal points out an essential and alarming feature of the politics of education: It's the one place where Democrats and Republicans have been willing, even eager, to embrace the same ideas.
America applies 311s "in a political way", says Jason Sharman, an expert in financial crime at Australia's Griffith University, even if some or all of the recipients have indeed done what they are accused of.Another alarming feature of 311s is that there is no requirement to make detailed evidence public, or even available to a court, to justify the action.
The use of children, especially girls, as suicide bombers has become one of the defining and alarming features of the conflict".
Syria's civil war has been especially dangerous for health professionals; a United Nations report issued last month described the "deliberate targeting of hospitals, medical personnel and transports" as "one of the most alarming features of the Syrian conflict".
The contagion caused by spiralling borrowing costs leaping from one country to the next was one of the most alarming features of the crisis and it explained how problems in tiny Greece could threaten the single currency as a whole.
In addition to evidence of impact craters in close proximity to Internally-Displaced Person (IDP) shelters, the final analysis reveals two new alarming features: Large gravesites and evidence of mortars used in and around the so-called civilian save zone.
The second, perhaps more alarming ad, features a Major Payne-esque drill sergeant screaming "wetter is better" in the face of a group of children, who then shoot him with the technical-sounding Super Soaker XP-105.
