Greece's likely new prime minister, the charismatic Alexis Tsipras, has been described as a "fiery" politician, a "dangerous ideologue," and even a "serial killer" -- a wily operative who ruthlessly elbowed his way to the top. His Syriza party has been cast as a radical, anti-establishment outfit, whose stubborn socialist agenda may plunge Europe into crisis.

But, after winning a near majority in Greece's parliament following elections on Sunday, Tsipras and Syriza can take control of the narrative. They have emerged as Greece's most influential political force in the wake of half a decade of grinding austerity measures, mandated by the European creditors who bailed out the debt-ridden Greek economy. The country's economic output has since shrunk by 25 percent; its unemployment rate stands at a staggering 26 percent.

"The verdict of the Greek people ends, beyond any doubt, the vicious circle of austerity in our country," the 40-year-old Tsipras told a jubilant crowd in Athens.

A Greek government led by Syriza -- a historic achievement for this coalition of former communists and socialists -- would confront what Tsipras deems an untenable status quo entrenched by successive center-left and center-right governments that did Europe's bidding.

"There are many people in this country searching through the trash for food or whose homes no longer have electricity," said Tsipras in an interview with a Greek journal late last year. "The real economy is in shambles, and unemployment has skyrocketed. Our young people consider emigrating their first option. And the possibility of being stuck living under these conditions for the foreseeable future is all too real — trapped by austerity and recession, without decent wages or work, without dignity."

Tsipras and his allies have made no secret of their intentions: a revival of the welfare state that would see wages rise, public sector jobs return and a raft of other reforms enacted to bring "hope" -- as Syriza's campaign slogan promises -- to ordinary Greeks. This stimulus will require Greece's lenders to consider writing off a chunk of its considerable debt and therefore presents the first showdown between a new leftist government in Athens and the European establishment, including German Chancellor Angela Merkel.

"We will seek to have a large part of the debt waived, and the repayment of the balance subject to a growth clause. You can’t repay a debt if you’re not allowed to work," Tsipras said last year, pointing to a historical parallel when post-war Germany's debts were halved at the 1953 London Conference. "This was exactly the logic that was applied to Germany’s debts after the Second World War."

It's still too early to tell what sort of compromise, if any, may be negotiated in the weeks and months ahead. (The European Central Bank has already signaled its unwillingness to renegotiate the terms of its multi-billion dollar loan to Greece.) But Syriza's leaders are adamant that this confrontation is necessary. The toll of austerity, argues Yanis Varoufakis, the economist tipped to be Tsipras's finance minister, "has been detrimental to Europe as a whole."

Speaking to U.K. television channel Channel 4 News, Varoufakis described himself and his Syriza colleagues as "reluctant" leaders, swept into power to fix a broken system. In his crosshairs are the country's oligarchs and banking elites, buttressed for decades by the country's complicit political establishment. These are, in Varoufakis's view, "forces that are essentially depriving democracy of its substance."

It's rhetoric that echoes Tsipras, who regularly inveighs against the ethos of "neoliberalism" that fuels the project of the European Union as well as the catastrophic recession which hit the eurozone five years ago. And it's rhetoric that has increasing traction across the continent, with populist, anti-austerity parties gaining ground in numerous countries.

There's a strong current of frustration with Brussels technocrats and feckless political elites running throughout Europe. Tsipras has said he wants to harness this mood in "favor of labor," and that "Syriza aspires to be the catalyst for these changes, creating a domino effect" through Europe.

Syriza's victory was celebrated in Athens by tens of thousands of ordinary Greeks. Joining them were, Italian, Tunisian, and German leftists waving red flags, a sign of how international the anti-austerity movement has become.

It was hailed by the official Twitter account of Podemos, the left-wing, anti-austerity party in Spain that, within the space of a year, has emerged out of nowhere to challenge Madrid's two-party status quo. The tweet quoted the Podemos leader, Pablo Iglesias, who as my colleague Griff Witte reported, had earlier participated in Tsipras' final pre-election rally. "The Greeks finally have a Greek government, and not an envoy of Merkel," the tweet reads, referring to the German chancellor who, as the leader of one of Europe's biggest lenders, is the bogeyman of anti-austerity campaigners.

Moreover, Tsipras and other European leftists know they aren't the only parties raging against the establishment. The far-right Golden Dawn party, which many consider to be a neo-Nazi organization, came in third in Greece's polls. In Britain and France, anti-immigrant, ultra-nationalist parties have made significant strides in recent European elections. While their views on the mandates of the E.U. and IMF may dovetail, they are worlds apart on other issues of social policy and multiculturalism.

"Unless the forces of progress and democracy change Europe, it will be Marine Le Pen and her far-right allies that change it for us," Tsipras wrote last week in the Financial Times, referring to the influential leader of France's far-right National Front.

Le Pen, ironically, offered her support to Tsipras and Syriza ahead of Sunday's election.

Read more:

How Greece's triumphant leftists want to change Europe

A young, impatient leftist is Greece's new defiant face