On Saturday, outgoing president Benigno Aquino launched a fierce verbal attack on the insurgent candidate, likening his rise to that of Adolf Hitler. "I need your help to stop the return of terror in our land. I cannot do it alone," Aquino implored. "We should remember how Hitler came to power. If you allow them to oppress your fellow man and you do not speak up, you will be the next one to be oppressed."
Duterte responded by dismissing Aquino as a "son of a wh***".
As a self-proclaimed womaniser, Duterte has peppered his campaign speeches with boasts about his viagra-fuelled sexual exploits. Last month, he came under fire for joking about the rape of Australian missionary Jacqueline Hamill, who was gang-raped and murdered in his city.
The remarks were made at a campaign rally, with a video being posted on YouTube and widely shared on social networking sites.
"There was this Australian lay minister ... I saw her face and I thought: Son of a b***h. What a pity ... they raped her, they all lined up," he told the crowd. "I was mad she was raped but she was so beautiful. I thought, the mayor should have been first," he said, recalling the riot by inmates at the Davao jail in 1989, where he has served as mayor for 22 years. Five missionaries were murdered by the detainees in the riot.
Duterte later refused to apologise for his comments.
Australia's ambassador in Manila, Amanda Gorely, condemned Duterte's remarks on Twitter.
On Saturday at his final campaign rally in Manila, he told a huge cheering crowd: "All of you who are into drugs, you sons of b***es, I will really kill you. I have no patience, I have no middle ground, either you kill me or I will kill you idiots."
He then vowed to execute 100,000 more criminals and dump their bodies in Manila Bay.
Outspoken TV host John Oliver took aim at the tough-talking political maverick during Sunday's opening segment on Last Week Tonight. Introducing him as a "colourful character, to say the least," the comedian played an Al Jazeera segment showing the mayor at a recent mass wedding.
From the stage, he offered himself to the brides as a wedding gift. "I don't have money to give, but I could give your wives something else, and this is for the wives only," Duterte says in the clip. "Men, I'm sorry, but you don't get anything, because I'm not a queer."
Oliver went on: "That's just the tip of the iceberg. Duterte routinely kisses his female supporters, once called the pope a 'son of a bitch', all of which has earned him a reputation of the 'Trump of the East' - a title previously held by a burnt wonton covered in scarecrow pubes.
"Duterte has also suggested, if elected, he would kill five criminals every week - which may not be an idle promise as since he's been mayor, extrajudicial death squads have reportedly killed over a thousand people. And while he denies any involvement in that, he does admit he has blood on his hands."
The political commentator then threw to a televised interview of Duterte admitting that he had killed people in the past. "Yes, of course. I must admit I have killed," he told the interviewer. "Three months early on I killed about ... three people."
Oliver commented: "I'm sorry ... about three people? That's not good! Not knowing how many people you've killed is like not knowing how much Vicodin you took: If you don't know the exact number, the answer is way too f***ing many."
In a nation weary from poverty, violent crime, corruption and insurgencies in the hinterlands, voters are looking for a radical change at the top. Duterte has tapped into that sentiment of discontent by brazenly defying political tradition, much as Trump has done in the US. His supporters see him as an authentic man of action and appear willing to overlook his talk of extrajudicial killings and unashamedly crude language.
Financial market analysts are predicting that a Duterte win would weaken the Philippine peso given his uncertain economic platform.
At least 15 people were killed during election-related violence during today's voting, and more than 4000 people arrested for violating a gun ban, police said.
