Even though a President has certain powers, that does not give him the right to abuse it.
Tell that to Bill Clinton, who set almost a dozen terrorists who murdered Americans just so their community would vote for Hillary and she could become a Senator.
Tell that to Obama who illegally spied on Americans, reporters, the media, US Senators, and the USSC...who illegally used the IRS as his own personal political weapon against Americans who did not support his ideology and re-election...who refused to enforce US law and aided those who broke it...who dragged the US into 2 Un-Constitutional Wars to help terrorists take over their own nations, who set free the mastermind responsible for the deaths of 4 Americans in Benghazi, and the Taliban 5 - the leaders of the enemies we are fighting a war against.
Trump pardoned a law enforcer who was found guilty of Contempt of Court, who far less violated Americans Constitutional Rights than Barry ever did, Trump stayed within the confines of his powers as President. he did not abuse his power by pardoning Arpaio, even if it is your biased opinion that he did.
You don't like that he pardoned him? Duly Noted. That doe not make what he did illegal or an abuse of power.
An abuse of power is illegally spying on Americans, the US Senate, and the USSC...illegally using the IRS as a personal political weapon, is illegally sharing classified information and unmasking Americans for Democratic Party political benefit.
Try bitching about something that actually IS an abuse of power rather than something that offends you / your opinion.