Sen. Elizabeth Warren, D-Mass., had some choice words about the GOP's tax reform bill unveiled on Thursday.

In an interview on CNBC's "Closing Bell," Warren called the tax plan a "$2 trillion giveaway to giant corporations" and added that the biggest beneficiary would be Wells Fargo, the bank at the center of a massive fake-accounts scandal last year. She also said beneficiaries include foreign investors and multinational companies.

"This gives real subsidies to move jobs overseas," she said, adding she would "do my best to stop it."

On the nomination of Jerome Powell to succeed Janet Yellen as the next Federal Reserve chairman, Warren said it's a good sign that he has aligned himself with Yellen. Still, she plans to reserve judgment until after the nomination hearing.

"I'm going to ask him some tough questions and hear what his answers are," she said.