Angela Merkel’s “farewell visit” to the Kremlin on Friday will mark the end of one of Europe’s oldest and most complex political relationships, a tense 15-year tug-of-war between Europe’s elder statesperson and the bloc’s chief antagonist in Vladimir Putin.

Though deeply strained, their relationship never snapped. The German chancellor was reportedly distrustful of the former KGB officer from his first appearance in 2001 before the Bundestag, where he wooed MPs in fluent German as he called for unity against international terrorism.

The two never looked quite comfortable in conversation, whether in German or Russian. Both formidable leaders, their clashing political styles and visceral distrust for each other made their summits compelling viewing.

“No other politicians on the global stage have been so good at getting on badly over such a long time as these two,” wrote Germany’s Suddeutsche Zeitung newspaper in an article before Friday’s summit.

Merkel’s early wariness of Putin has been justified by the events of the past 15 years, from Russia’s annexation of Crimea to the poisoning attack on the dissident Alexei Navalny and assassinations in Europe.

There were personal slights too, such as an incident in 2007 when Putin allowed his labrador Koni to approach Merkel, who has a fear of dogs. “I understand why he has to do this – to prove he’s a man,” she told a group of reporters after. “He’s afraid of his own weakness.”

And yet, as many in the west have sought to isolate Putin, she and France’s Emmanuel Macron have urged EU nations to maintain a direct dialogue with the Russian leader. As she enters the twilight of her term in office, allies of the Russian president believe Merkel will seek a breakthrough in talks on conflict in Ukraine when she meets with Putin on Friday.

But what scope there is for cooperation remains unclear. The Minsk dialogue – the peace talks largely shepherded by Merkel between Ukraine, Germany, France, and the Russian-backed separatists in southeast Ukraine – are deadlocked.

And the meeting comes on the one-year anniversary of the poisoning attack on Alexei Navalny, the Putin opponent imprisoned in Russia in a case clearly motivated by political revenge. It was Berlin’s Charite clinic that confirmed he had been targeted with a novichok poison last year, a diagnosis Russia has rejected.

“This still unresolved case of course puts great strain on our relationship to Russia,” Merkel spokesperson Steffen Seibert said on Wednesday. “Our demands have still not been met. You will also know that Mr Navalny is unjustly imprisoned, spends his sentence in a penal camp and that there are even new charges being raised against him. All these points weigh on the relationship between Germany and Russia.”

Other critics see Merkel as far too soft on Russia. Her final visit comes as Nord Stream 2, a pipeline that links Russia to Germany, nears completion. The pipeline, which will allow Russia to deliver gas directly to Germany and bypass other countries that it currently uses for transit, has put eastern Europe on edge.

Volodymyr Zelenskiy, the president of Ukraine, has called the pipeline a “powerful weapon being given to Russia”. He was reportedly “surprised” and “disappointed” after the US and Germany announced they had reached a deal to allow the pipeline to go ahead.

Merkel has said Germany will respond if Russia uses the threat of gas cutoffs to pressure Ukraine and she is scheduled to visit Kyiv on Sunday in what appears to be an attempt to allay concerns. The Atlantic Council, a thinktank strongly critical of Russia, has called on her to use the visit to “reject Russia’s imperial claims to Ukraine”.

Merkel is likely to phrase it differently when she meets Putin for the last time as chancellor this week. She has said she challenges the Russian president directly in private, adding: “When it comes to criticism of him, I don’t hold back.”

But her calls for direct talks with Putin, also supported by Macron, are increasingly facing a backlash in the EU, where some believe the Russian leader cannot be reasoned with.

“Overall, we have a lot of conflicts with Russia that unfortunately make our relationship very difficult,” she told the Parliamentary Assembly of the Council of Europe in Strasbourg earlier this year. “Nevertheless, I am someone who says we must always talk.”