Folks always seem to forget that "realpolitik" basically means "do stupid, shortsighted, usually just kinda' evil shit for reasons" and then get all surprised pikachu when the people involved with it do stupid, shortsighted, evil shit. Backstabbing bastards that ruin most everything they touch, like kissinger, are idols of realpolitik, because that's just kinda' what that nonsense is, a big ol' pile of razor laced shit terrible people have tried to gild with gold so other people don't realize what's being handed to them.
Kissinger is the inbred incest baby of realpolitik. People like Bismarck defeating the Austrians in war, but then demanding no land from them is I think perfect examples of realpolitik as "pragmatic policy." Because he could have seized land from the Austrians, yet in doing so made a long term enemy of them, whereas the potential of an Austrian alliance gave him the freedom and flexibility to negotiate with the French, Russians and British who would not have a hostile Austria to exploit.
Declining the small, short-term game of gaining Silesia for example, they gained the potential of the whole state. Ppl like Sun Tzu or Bismarck advocating for trying to achieve your aims with the threat of a campaign, whilst avoiding an actual war, or ppl like Machiavelli saying that you should build a reputation of trust and loyalty for
pragmatic reasons rather than ethical ones, miss the point by going full Kissinger. It is not brave or intelligent to betray someone who is not guarding against you because they called you friend, but somehow the whole message of "virtue as pragmatic" gets lost on the team killing fucktards. Machiavelli doesn't judge someone who comes to power through villainous, murderous means - but he cautions that if they were to launch a bloody coup, it would be best to eliminate all of their enemies in one day and then forswear ever resorting to tyranny and violence ever again. Because on
pragmatic grounds, people can eventually grow accustomed to someone who is reliable, stable and stalwart, whereas a tyrant who never stops killing is going to have all of his followers thinking "am I next to die?" And he cautions again, that you really ought not to try gain power through villainous means, citing an example of one usurper who did kill all of his enemies in one day, yet was beaten to death by the townspeople who much loved the nobleman he had murdered. All examples of "look, putting moral concerns aside, pragmatic power must still take morality into account."
An army known for being merciless will fight to the death and can inflict terrible casualties on an attacker. Thus Sun Tzu advises either encourage enemies to surrender through clemency, or leave a way out for the enemy to encourage a rout. An ally who allies with a greater power to betray their weaker ally in exchange for short term gain (something Machiavelli personally witnessed often with the feuding Italian states) will soon be left with a great ally who no longer needs them independent; whilst the only other ally who can now help them resist conquest, is the one they just betrayed. Thus Machiavelli advises not betraying your allies, even when they are weaker than you. For today they need you, but tomorrow you may need them. Against Denmark, Austria and France, Prussia scored monumental military victories. Yet Bismarck restrained his own conservatives, hungry for triumph and conquest, arguing that an attempt to dismember and cripple France or Austria would simply leave them with powerful, irate foes, and at any rate the British and Russians would not abide by such a disturbance in the balance of power. The one time he buckles to public opinion and annexes Alsace-Lorraine, the same fears which cautioned him not to annex territory from Austria proved true in France: the French would accept any peace, except one which saw the loss of territory. And so for the next 20 years he contented himself with keeping France diplomatically isolated, securing concessions from Russia and Britain with the threat of action, and yet made no attempt to pursue continental hegemony on the eve of victory in the manner of Napoleon. He would've been rolling in his grave to find out after his death, that any attempt to diplomatically isolate France had been thrown out of the window by an attempt to challenge the Royal Navy in the North Sea and Russia in the orient without any real plan or thought as to "what happens if they all ally?" Because pissing people off all at the same time is... Inadvisable.
The thing about realpolitik as a concept is it usually means being pragmatic and ignoring one's ideology when it gets in the way of being effective. The positive image of this one thinks of is when one comes to a mutual agreement despite being ideologically opposed (example: a good chunk of why the cold war didn't go nuclear). For the negative of course, when the ideology or other "on paper" policies being ignored are things like basic common sense, international agreements, or the laws of war...
As seen here however, another layer to this is a lot of politicians don't really understand the word "pragmatic" and instead take it to mean "bumblefuck my way over everybody in my way to get a paycheck, consequences be damned"
See also: CEOs and Presidents running their companies/countries into their ground because they think running their organisations/nations like mafia loot goblins makes them intelligent