What is the opposite of breaking the news gently, without being mild or considerate, just giving it to them bluntly and being straightforward.
Consider laying it on (someone), an idiom which means:
To tell; inform
It connotes bluntness and straightforwardness, at least more so than break the news gently.
The straightforwardness connotation can be seen in the definition from Urban Dictionary:
tell me what you're saying, be more clear, or tell me something.
Another suggestion is hit (someone) with it, an idiom which means something like:
reveal or do something shocking to someone.
It has its root in the following sense of hit:
informal Be affected by (an unfortunate and unexpected circumstance or event)
Here are example sentences involving both idioms:
- His grandmother had died. At the breakfast table she laid it on him.
- She hit him with the news of his father's death.
In the first verse of I Don’t Want To Hear Anymore, The Eagles seem to oppose the notion of “Telling it like it is” with that of “breaking it gently”:
I know you're trying hard
To break it gently to me, now
But there's no easy way
To tell it like it is, so baby ...
(lyrics, with emphasis added, retrieved from Genius.com)
Inf. Speak frankly.; Tell the truth no matter who is criticized or how much it hurts.
“Come on man, tell it like it is!"
"Well, I've got to tell it like it is.”
(from McGraw-Hill Dictionary of American Idioms and Phrasal Verbs via The Free Dictionary by Farlex)
Give it to them straight i.e. getting straight to the point, saying it clearly, succinctly, honestly and without unnecessary sugar coating.
There are also metaphors you could try such as rip of the plaster (or bandaid) - pulling off a plaster can be less painful if done in a single quick motion - "Just rip off the plaster, tell me straight, am I going to die?"
Not pull any punches
to speak in an honest way without trying to be kind: Her image is that of an investigative reporter who doesn't pull any punches.
(Definition of “not pull any/your punches” from the Cambridge Advanced Learner's Dictionary & Thesaurus © Cambridge University Press)