Pelosi has shown the strength of her leadership time and time again. During her first term, she oversaw landmark legislation like Obamacare. Several Democratic presidents tied and failed to pass meaningful healthcare reform before Obama. It was thanks to Nancy Pelosi's deft handling of the House of Representatives that gave Obama the votes he needed. Despite criticism from the left-wing of the Democrats, Pelosi has shown that she knows how to conduct politics.
Pelosi has been cast as one of the central villains against Trump. Republicans see her as one of the main Democrats determined to sabotage and undermine the President. They say she is power-hungry and an obstructionist, emblematic of the Washington D.C. politician.
On the other hand, some Democrats think Pelosi represents everything currently wrong with the Democratic Party. Her leadership is actually hollow and cowardly because she's failed to take action when it really counts—her failure to impeach President Bush for lying to start the Iraq War was a huge, colossal failure.