Hillary Clinton addresses Service Employees International Union (SEIU) members at the group's 2016 international convention in Detroit, Michigan, on May 23. REUTERS/Rebecca Cook Democratic presidential frontrunner Hillary Clinton targeted her likely Republican rival at a Detroit event on Monday, calling him a "bully" and charging that he'd "bankrupt America."

Donald Trump, the presumptive Republican nominee for president, has been looking toward the general election and targeting Clinton recently as he has surged in national polls.

Now, Clinton is returning fire by attacking Trump on his business record, immigration policies, economic policies, and supposed "bullying."

NBC News called it "the best preview yet of her campaign's general election strategy."

Here are some of the attacks Clinton mounted on Trump at the Service Employees International Union's annual convention:

"H e could bankrupt America like he's bankrupted his companies. Ask yourself: How could anybody lose money running a casino? Really." Clinton was apparently referring to Trump's Taj Mahal casino in Atlantic City, New Jersey.

e could bankrupt America like he's bankrupted his companies. Ask yourself: How could anybody lose money running a casino? Really." Clinton was apparently referring to Trump's Taj Mahal casino in Atlantic City, New Jersey. "We need a president who will use the bully pulpit to stand up for working families. But the last thing we need is a bully in the pulpit."

"What kind of country would we be if we let Donald Trump rip our families apart? We have to reject this wrong vision for America with a strong, clear voice."

"A lot of Republicans themselves say Donald Trump is a disaster waiting to happen to America."

"What little we know of his economic policies would be running up our debt, starting trade wars, letting Wall Street run wild. All of that could cause another crash and devastate working families and our country."

"Trump economics is a recipe for lower wages, fewer jobs, more debt."

Trump has been relentless with his attacks on Clinton in recent weeks. On Monday, for instance, he posted a video on his Instagram account featuring interview clips of women who have accused former President Bill Clinton, Hillary's husband, of sexual misconduct. The clip asked whether Hillary Clinton was "really protecting women."

At a National Rifle Association event on Friday, Trump attacked Clinton over her gun-control policies and claimed that she would "abolish the Second Amendment."

Trump has also gone on several tweetstorms about Clinton, often referring to her by his preferred moniker: "Crooked Hillary."