Superman may be a dick sometimes, but even he pales before the Taxman. Nooo, thank you! This is especially odd when said characters handle Eldritch Abominations on a regular basis and are able to kill an army like it was nothing. Apparently, going to jail for tax evasion is a Fate Worse than Death. On the plus side, they help the reader relate to the character because taxes are serious business in Real Life and can even make the villain more sympathetic, pitting them against the unfathomable might of Even gangsters who get away daily with murder and robbery may fall into the clutches of the law, dead or alive, if they don't pay their income tax.
In fact, that actually happened to Al Capone. Sometimes, the intimidating part comes from a person who gets a summons to the tax office and the person fears that they are in trouble and might be arrested for a tax violation.
In this kind of story, it turns out the bureaucrat is a nice enough person who just wanted to clear up a minor problem and, seeing that the character is frightened, has to give some reassurances that nothing is wrong beyond that.
A few times, the "intimidating" part is literal: the IRS agent is a highly antagonistic , inhumanly slimy Evil Debt Collector who is itching at the possibility of sentencing the protagonist to fifty years hard labor in Leavenworth or the chair and seizing literally everything the protagonist has for the crime of owing Uncle Sam and the IRS agent ten cents.
Or to avoid having to sign a check to pay the protagonist back said ten cents. Based on His Majesty's Inland Revenue department now His Majesty's Revenue and Customs depending on the current British monarch's gender , it was founded shortly after the beginning of the USA's Civil War as part of the process of full economic mobilisation required to build up and sustain an army big enough to suppress the rebellion.
