Last July, it was Moro who condemned the seemingly invincible leftist icon to more than nine years behind bars for taking bribes and laundering money following an almost unprecedented corruption investigation known as "Operation Car Wash."
In January, the sentence was increased by an appeals court to more than 12 years.
The conviction of Lula, who served as president between 2003-2010, sent a chilling message to the country's deeply corrupt political elite.
And on Thursday, the 44-year-old magistrate struck again, giving Lula just 24 hours to turn himself in or face forcible arrest and begin serving his jail term in Curitiba, the southern city where the massive anti-graft operation has been based since launching four years ago.
It was one of Moro's most explosive decisions since taking over the sprawling probe which initially centered on Petrobras, the flagship state oil company, but which has since expanded to embrace Brazil's economic and political elites.
Headed by Moro, the investigation has become one of the world's biggest corruption battles, tackling business empires like Brazil's Odebrecht construction group and reshuffling the political deck ahead of this year's presidential election.
Exposing a vast embezzlement scheme centered on Petrobras, Moro was quick to jail almost all of the oil giant's former directors, before turning his gavel on the powerbrokers at Odebrecht, leaving no one untouchable.
This led him to the dirty money being pumped to the world of political campaigning, with the scandal touching most of Brazil's political parties. Moro swiftly moved to take down a string of top-level players from across the political spectrum.
And Lula, who is being prosecuted in seven separate cases, is his biggest scalp yet.
'Can make anything happen'
In March 2016, the spotlight turned on Lula when he was questioned on Moro's orders about "favors" he allegedly received from firms implicated in the scandal.
Lula knew that Moro, who is based in provincial Curitiba, more than 1,000 kilometers (600 miles) from Brasilia, was serious.
"Honestly, I'm scared of this 'Republic of Curitiba' because a district judge can make anything happen in this country," Lula could be heard saying in a leaked phone conversation last year.
Born in August 1972 in Maringa, a city near Curitiba, Moro went on to study law, gaining a doctorate and becoming a federal judge in 1996.
He completed his training at Harvard law school, going on to specialize in money laundering crimes and taking inspiration from Italy's "Clean Hands" anti-corruption drive in the 1990s, which led to the conviction of half the country's lawmakers.
In a 2004 article on this operation, Moro sketched out what would become the method that thrust him into the global limelight 10 years later: getting detailed confessions from suspects in exchange for a reduced sentence, as well as leaking elements of the probe to the press.
"Moro has instituted preventative detention as the norm, whereas in any other civilized country, it is the exception," said lawyer Antonio Carlos de Almeida, who was on the Petrobras defense team.
Hero to millions
A married father of two, Moro's unprecedented assault on business-as-usual has elevated him to hero status among most Brazilians, who see him as a knight in shining armor in the fight against the country's rampant corruption.
His stern face has even become a standard feature on banners and t-shirts at corruption rallies around the country, with supporters seeing him as a future Supreme Court justice or even president.
But the tough-talking judge is rarely seen on the streets of Curitiba, and prefers to avoid public appearances. And on the rare occasion when he has ventured out, it was to ask his "fans" to exercise restraint ahead of his historic confrontation with Lula.
And though he has denied having any political ambitions, the latest Datafolha poll ahead of October's presidential election show that if the vote were held now, the Moro would be one of the only figures who would likely beat Lula.
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