What about Erdogan and Gülen (although Gülen created a whole movement) ?

@SdaliM Or Erdogan and German comedian Jan Böhmermann. Although this one appears to be more personal than political.

@Philipp Yes, I forgot about that story. This leads me to think that there are two categories in this question: when the leader criticizes a person from its country, and when it's a foreign one.

I've voted to close this question as too broad. There is a quality question in the soup, but as it stands there isn't a referential metric for "how common."

@DrunkCynic yes, that's exactly why I'm asking this question. I don't know what kind of "better" question to ask instead.

Nixon and his enemies list Wiki

@KDog Anecdotal evidence doesn't answer the question, it just invites a massive summation of the times where a Political Leader has targeted a citizen. It would take a sizeable evaluation of every government in history, detailing their foundational structures that empowered the Political leader to target a single citizen, generating a probabilistic relationship between personal attacks and government structure, such that the likelihood of attacks could be predicted with given factors.

@DrunkCynic I agree. The question needs some boundaries. However, the link I posted goes into greater detail how rare this is in the US. I couldn't really address in a comment, but thought the link might help the reader/questioner.

@KDog - The person referenced in the article talks about the 2012 campaign, and the citizen that was singled out was a chairperson of Mitt Romney's national campaign finance committee. So he was a member of the Romney campaign, not just a "private citizen."

@PoloHoleSet - he was an employee. Being an employee of a non-private citizen doesn't automagically make you non-private citizen.

Obama singled out Koch brothers repeatedly. French politicians singled out Gerard Depardeu when he fled the country to escape 90% taxes. Putin did that repeatedly.

@DrunkCynic - a question that's a meaningless "this must be a bad thing and nobody else does it, amirite" is perfectly well answered by "nope, it's been done before, including by the polar opposite of the leader your question tries to denigrade stealthily - example".

Ah, good examples. Probably should clarify that anyone in the forbes #10 richest people in the world wasn't the kind of regular citizens I was thinking about when I asked the question.

@user4012 - being one of the top level people in a presidential election campaign DOES. So, no, he wasn't an "employee," as if he worked for a business venture that Romney happened to be involved in. He was one of the top organizers on Romney's election campaign, which means you are going to be talked about by the other campaign during the actual election campaign you are involved in. That's such nonsense to pretend otherwise.

@PoloHoleSet - He wasn't running for office. Period.