Idiom for 'person who gets violent when drunk"
In Portuguese, the expressions "ter mau vinho" (have bad wine) and "ter mau álcool" (have bad alcohol) refer to people who become violent when they drink too much. Typically, these people are considered nice and even kind when sober, but become aggressive or violent after a few (or too many) drinks.
It's usually used in dialogue similarly too:
Daniel? Oh, he 'has bad alcohol'. I wouldn't go drinking with him, if I were you.
or
Daniel is such a nice guy! I'd never have thought he 'has bad alcohol'.
Is there a similar idiom in English?
A "mean" drunk
...describes someone who gets aggressive when drink taken.
Why People Get Mean When They're Drunk, According to LiveScience.com:
There may be a mean drunk inside every man — and now scientists think they might know why.
According to a new paper published in the February issue of the journal Cognitive, Affective & Behavioral Neuroscience, MRI scans of drunk and sober men show that alcohol-related changes in the prefrontal cortex — the region of the brain thought to be responsible for moderating social behavior and aggression, among other executive functions — may be responsible for booze-induced anger.
Also, we have:
Personality Trait Reveals Who Becomes a Mean Drunk
Drinking can make some people more aggressive, and now researchers have found a particular personality trait — a focus on the present, with little regard of consequences — that appears to make someone under the influence more likely to become mean.
So you could say:
"Daniel is such a nice guy. I would never have thought that he is such a mean drunk."
Also see:
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Why alcohol can turn you into a mean drunk
-
Mean Drunk: Anger, Hostility and Alcohol
-
I'm Out of Here: The Memoir of a Drunk
As you can see, it is used both formally and informally.
Daniel is such a nice guy, but gets belligerent when he drinks.
This is the term I've most often heard in the United States, especially among younger generations, to describe a person who becomes angry and / or violent when drunk.