Duterte, 71, won the presidential election in May by 16 million votes, or about 38%, an unassailable lead that forced his three opponents to throw in the towel one after the other.
Promising that "change is coming" Duterte -- called "the Punisher" for going after alleged criminals and drug dealers -- captured the imagination of the masses long suffering from chronic corruption and high crime.
In his speech he highlighted the country's problems of corruption, criminality, drugs and the erosion of faith and trust in government.
"Change must start with us and in us. We have become our own worst enemies, and we must have the courage and the will to change ourselves," he told the 600-strong crowd.
"I know that there are those who do not approve of my methods of fighting criminality... In response, let me say this: I have seen how corruption bled government of funds. I have seen how illegal drugs destroy individuals and ruin families' relationships.
"I know the limits of the power and authority of the president. I know what is legal and what is not. My adherence to due process and the rule of law is uncompromising."
A rocky start to leadership
In the lead up to his inauguration, Duterte went on a war path with the dominant Catholic Church, accusing its bishops of doing nothing but enrich themselves. He also launched a blistering attack against the national press,
publicly accusing them of being biased against him.
During one of his speeches he falsely accused a reporter of allegedly being biased because he asked him about his health. In the past two weeks, he has shunned press coverage, and has even barred the independent press from covering his inauguration.
In a pooled editorial Wednesday, the country's leading newspapers noted that the conversation between Duterte and the news media has regrettably "turned sharp and shrill."
Whether intended or not "his volcanic language has dampened, indeed chilled, the daily coverage, so that journalists with valid, if testy, questions are seemingly forced to eat expletives by way of a response," the editorial said.
"Duterte's troubled relations with the media is partly a reflection of the irreconcilable philosophy of the mainstream press in the country, which tends to focus on the glass half empty, and the incoming president's preference, where the media is an amplifier for the voice of the leader rather than its detractor," said Richard Heydarian, a political analyst at the De La Salle University.
Duterte was "one of those bolt-from-the-blue populists" who by downgrading the establishment and promising change had "to make all sorts of mostly unrealistic promises," Heydarian said.
Those promises, which struck a chord among the wary population, include reintroducing the death penalty. Duterte has also vowed to dump bodies of dead criminals on Manila Bay.
The president told police in speeches during his campaign that he will protect them from prosecution, and thumbed his nose at rights advocates.
And it appears the police has tacitly followed his instructions, reporting that at least 40 suspected drug dealers have been killed in encounters since Duterte was elected, compared to just 39 in the four months prior.
"There's a danger that Duterte's electoral victory may be interpreted by some as a symbolic victory for a notion that's already spreading in the Philippines: that extrajudicial vigilante-style killings of suspected criminals is a legitimate approach to crime control," Phelim Kine, deputy director for Asia of the New York-based Human Rights Watch (HRW) told CNN.
He said Duterte's statements "before, during and since the presidential election have raised grave concerns that his administration will result in a serious regression of human rights."
Kine said HRW was looking forward to hear from Duterte that such statements "were electoral season bluster" than serious policy statements, because as soon as he steps into office "he is obligated to extend the human rights protections embodied in the constitution to all the people of the Philippines — even those he considers "criminals.'"
"As President of the Philippines, Duterte will be entrusted with ensuring the protection of the universal rights and freedoms of Filipinos and he therefore needs to be a symbol of rule of law rather than of violent, extrajudicial methods which undermine it," Kine stressed.
Duterte's chosen cabinet includes an eclectic array of politicians, including leftist leaders and former officials with good track records.
His hand-picked national police chief, too, is man known for his tough approach to criminality who goes by the nickname "bato" or "stone." However, the president also received praise for launching peace talks with communist rebels even before he assumed office.
Duterte meanwhile has also appeared to have surrounded himself with a good economic team, composed mostly of "seasoned technocrats" who could build upon the gains of Aquino, who is largely credited for stabilizing the economy when most in the region were stumbling.
There are, too, hopes that his election will bring, once and for all, elusive peace and stability in the south, which for years has been rocked by Muslim militancy.
While a peace deal has been struck by Aquino with the country's largest Muslim rebel group, a smaller band of militants called the Abu Sayyaf
continues to be a problem.
The group has recently beheaded two Canadians taken hostage last year, but recently freed Filipina, Marites Flor
. A Norwegian man, Kjartan Sekkingstad, and a group of Indonesian sailors remain in captivity, separately.
"I think Duterte wants his legacy to be ultimately about bringing a semblance of peace and development to Mindanao, and his cabinet looks very promising in that regard," Heydarian said.
"But he has to be very careful with ensuring his 'war on crime' will not overstep his constitutional obligations and not come at the expense of broader national security."
"That will be a very difficult balancing act."