In a combative speech filled with insults, Trump mocks Biden’s Stutter and vilifies migrants and others.

Early in his remarks at what was effectively his first campaign rally of the general election, former President Donald J. Trump on Saturday blasted President Biden’s State of the Union address as an “angry, dark, hate-filled rant” that was more divisive than unifying.

Then, in the nearly two hours that followed, Mr. Trump, speaking in Rome, Ga., used inflammatory language to stoke fears on immigration, and repeated his false claim that the 2020 election was stolen from him.

The former president, who faces four criminal cases, called the press “criminals.” And he mocked President Biden’s stutter and revived a litany of grievances against political opponents, prosecutors and television executives.

Mr. Trump told thousands of his supporters gathered at the rally that “everything Joe Biden touches” turns to filth, though he used an expletive to describe the result. “Everything. I tried finding a different word, but there are some words that cannot be duplicated.” (He used the word, or a variant, at least four times in his speech.)

The former president’s speech in Georgia, a key battleground state that he narrowly lost in 2020, underscored that Mr. Trump is not likely to temper the ominous and at times apocalyptic vision that has animated his campaign, even as his last remaining Republican rival has dropped out and the general election has come into focus.

As he has in the past, Mr. Trump insisted that the biggest danger facing the United States was his political opponents, whom he labeled “the threat from within,” a turn inward that has alarmed experts for its similarity to language used by totalitarian leaders.

But in a speech replete with digressive rants, Mr. Trump reserved some of his most incendiary rhetoric to vilify migrants crossing the border illegally. Much of his speech was focused on immigration, an issue that he and his advisers have signaled will be central to his efforts to defeat Mr. Biden and return to the White House.

While vowing to expand his crackdown on immigration, Mr. Trump described the continuing surge of migrants across the southern border as “the agony of our people, the plunder of our cities, the sacking of our towns, the violation of our citizens and the conquest of our country.”

Mr. Trump also took aim at Mr. Biden’s policies on immigration, in part by using the Georgia setting to blame his rival for the death of Laken Riley, a 22-year-old nursing student who was killed in the state last month by, according to the authorities, a Venezuelan migrant who had entered the country illegally and had been released on parole.

Mr. Trump met with Ms. Riley’s parents before taking the stage, and the Trump campaign distributed signs at the rally with Ms. Riley’s photograph. During his speech, Mr. Trump accused Mr. Biden of neglecting the surge of migrants at the border, which he called a “deadly invasion that stole precious Laken’s beautiful American life.”

Mr. Trump often broadly casts those crossing the border illegally as violent criminals. “The migrants are hurting people,” Mr. Trump said. “They talk about the beautiful dream of migrants. It sounds so nice, you know, like in a fairy-tale book. But some of these people are monsters.”

Border authorities, including some who worked for Mr. Trump, have said that most of the migrants who cross the border are members of families fleeing violence and poverty.

But Ms. Riley’s death has become a flashpoint in the nation’s heated debate over immigration policy, in part because it seems to adhere to Mr. Trump’s long-stated belief that violent men from South America are flooding across the border to harm Americans.

“He was an illegal migrant, and he shouldn’t have been in our country, and he never would have been under the Trump policy,” Mr. Trump said of the man accused of killing Ms. Riley.

Mr. Trump also attacked Mr. Biden for expressing regret that he used the word “illegal” to describe the man accused in Ms. Riley’s death during an exchange at the State of the Union address on Thursday.

The speech that Mr. Trump gave on Saturday was his first since Mr. Biden repeatedly attacked him and his policies in his State of the Union address. “Joe Biden should not be shouting angrily at America,” Mr. Trump said. “America should be shouting angrily at Joe Biden.”

But his critiques moved toward personal insults. At one point, Mr. Trump slurred his words and pretended to stutter in a mocking imitation of the president, who has dealt with a stutter since childhood.

It was one of several such attacks Mr. Trump lobbed during the event. Of the former television anchor Megyn Kelly, with whom Mr. Trump sparred during his first presidential run, he said “may she rest in peace.” While talking about the success that his time on “The Apprentice” had brought NBC, he called Jeff Zucker, the network’s former chief executive, an “idiot.”

Mr. Trump also denigrated a number of prosecutors and judges involved in the criminal cases and multiple civil lawsuits in which he is entangled. He spent a considerable amount of time attacking Fani T. Willis, the district attorney prosecuting him over his efforts to overturn his 2020 election loss in Georgia.

Mr. Trump called Ms. Willis “corrupt,” referring to allegations that she benefited financially after becoming romantically involved with a lawyer whom she hired on the case. (Ms. Willis has pushed back against those claims, calling them full of “wild and reckless speculation.”)

He also repeated his false contention that he won in Georgia in 2020, maintaining that he had done nothing wrong when he called state elections officials, insisted that he had won Georgia and asked Georgia’s secretary of state to “find” the votes he needed to win.

“Perfect phone call,” Mr. Trump said, “other than we challenged the honesty of this election. This election was rigged.”

Maggie Haberman contributed reporting from New York.