On the evening Donald J. Trump reclaimed the presidency, he called for unity, stating that “it’s time to unite” and move past the last four years of division. However, this message of reconciliation quickly shifted; just 55 hours later, he began hinting at using his regained authority to investigate those who had opposed him.

Upset by what he labeled as “fake, untrue, and probably illegal rumors” about potentially selling shares in his highly profitable social media platform, Mr. Trump took to the internet, refuting such claims and demanding investigations into those spreading the gossip.

Whether or not Mr. Trump will act on this or any other threats to prosecute adversaries remains to be seen. Although he frequently lashes out without follow-through, he doesn’t always. His campaign was marked by promises of “retribution” for perceived wrongs, leaving both allies and rivals anticipating potential payback when he resumes office in January.

Returning to the White House eight years after his initial win, Mr. Trump arrives angrier, more embittered, and more vocal about seeking revenge than during his first term. His brief election night call for unity led some to speculate he might soften his tone. After all, he has achieved significant personal victories: validation by voters, a decisive win, and a likely end to any personal legal risk following a Supreme Court ruling granting sitting presidents immunity from prosecution.

But such interpretations may underestimate his desire for retribution after numerous impeachments, investigations, indictments, and lawsuits. While he may not pursue high-profile figures like President Biden or Vice President Kamala Harris, close allies expect him to target some of those he perceives as enemies. With Mr. Trump’s unpredictable nature, few feel confident assuming he won’t change his mind, contributing to a climate of potential intimidation.

“Will Trump retaliate?” asked Trump family biographer Gwenda Blair. “Certainly. The real question is how much will be broad and how much targeted.”

Blair suggests that, at the very least, Mr. Trump’s return will bring publicized congressional investigations, special prosecutors, and prosecutions. Quiet forms of retaliation could include audits, terminations, or cancellations of government grants, programs, and loans.

Mr. Trump’s office has not commented on whether he plans to pursue his promises. However, some advisers caution that his track record shows he’s unlikely to forgive or forget, describing him as an “eye-for-an-eye person,” still seething over events of the last four years.

Republican insiders reveal that Mr. Trump’s advisors are debating two paths. While some urge retribution, calling attacks against him “lawfare” that justifies a forceful response, others, including certain influential donors, argue that such actions could damage his legacy, advising him to focus on policies like tax cuts, tariffs, and immigration.

His choice for attorney general will likely signal his approach. Selecting an assertive figure like Matthew G. Whitaker, a former federal prosecutor, would indicate a focus on punishing adversaries. Alternatively, choosing Jay Clayton or Robert J. Giuffra Jr., both experienced in corporate law, could suggest a priority on policy goals like immigration.

In the days since the election, Trump’s more combative allies have eagerly anticipated a wave of retribution. Mike Davis, founder of the Article III Project, which supports conservative judicial appointments, took to social media, sharing that he hoped to symbolically “burn” political adversaries. He later clarified this would be “legally, politically, and financially.”

If Mr. Trump refrains from taking action through the Justice Department, Congressional Republicans may act on his behalf. Representatives Jim Jordan and Barry Loudermilk, both from the House, signaled they intend to scrutinize federal special counsel Jack Smith’s actions in the upcoming term, recently directing his office to preserve investigation records regarding Mr. Trump.

Over 100 potential investigation targets emerged during Mr. Trump’s campaign, according to NPR’s tally. Among those he pledged to prosecute are members of the Biden family, Vice President Harris over border policy, and former President Barack Obama, who he proposed trying in military tribunals.

Mr. Trump has further vowed to prosecute individuals responsible for his legal battles, including New York Attorney General Letitia James, Judge Arthur F. Engoron, and Manhattan District Attorney Alvin L. Bragg. He also threatened to fire special counsel Jack Smith, who charged him with efforts to overturn the 2020 election and mishandling classified documents, and possibly expel him from the country.

In addition, Mr. Trump has suggested prosecuting a Georgia grand juror who indicted him and promised “long term prison sentences” for election workers who he accuses of cheating him. He has said Meta CEO Mark Zuckerberg “will spend the rest of his life in prison” if found to have broken any laws.

Revenge has long been central to Trump’s philosophy. He once said, “If they screw you, screw them back 10 times as hard.” During his first campaign, he even told opponent Hillary Clinton during a debate that if he won, “you’d be in jail.” Although he softened his tone after winning, he occasionally returned to the idea of prosecuting rivals.

While in office, Mr. Trump’s efforts to involve law enforcement against opponents reached levels unprecedented since Watergate, though his attorneys general often resisted his demands. However, his administration did investigate those who angered him, including former FBI officials Andrew McCabe and Peter Strzok.

It’s unclear if Mr. Trump will investigate Mr. Biden, given previous Congressional inquiries into Biden’s family that failed to uncover impeachable offenses. However, some warn against assuming he won’t act on his impulses. “He’s erratic and has the attention span of a 7-year-old,” noted former Justice Department official Harry Litman. “But his thirst for revenge against those he views as his current antagonists is very real.”

In recent days, those presumed to be on Mr. Trump’s list of enemies have remained silent to avoid provoking him, with some, like retired Joint Chiefs of Staff chairman Mark A. Milley, concerned he could even be recalled to active duty for court-martial.

Though Mr. Trump’s angry social media posts about stock speculation in his social media company seemed primarily aimed at protecting his finances, his close allies are pressing him to act. Elon Musk, Trump’s billionaire supporter, reposted a video of the former president pledging to dismantle what he calls a “left-wing censorship regime.”

Mr. Trump has accused federal officials and social media platforms of trying to silence conservative voices, while they maintain that their aim was to counter misinformation about elections and vaccines. In the video, Mr. Trump vowed to direct the Department of Justice to investigate those involved in “online censorship” and prosecute any identified crimes, with Musk echoing his support by adding, “YES.”