Yes, Obama has been abusing his powers, because he take unilateral actions, for example, by not upholding Obamacare mandates that he, himself wanted. Obama also made inappropriate remarks rebuking the Supreme Court during a State of the Union address. This was bad decorum and an abuse of his powers. He rules by might, not right.
President Obama was elected with a majority in the electoral college in 2008. The Affordable Care Act passed with a majority in Congress. Every time it has gone to court, it has been found to be constitutional. The ACA was the major issue he ran on in 2012, and the people re-elected him. He has literally done everything regarding this issue by the book. Yet his opponents are constantly accusing him of overstepping his bounds. He isn't abusing his power; his opponents are sore losers.