He assassinated an American overseas without a trial. This particular American, as I understand it, was largely a propagandist.
This is fair. Its a very sketchy issue that needs more attention.
He lied to conservative democrats that there wouldn't be abortion coverages and things of that nature.
While you linked to a very biased source, this isn't technically wrong. I still fault those individuals for not knowing what was in the bill though, and nothing about this is unconstitutional.
He lied to people that if they liked their plan they could keep their plan.
He did, although I feel he took advantage of a particular wording rather than lied. Not unconstitutional however.
During the Libyan operation, he refused to report to Congress after a certain number of days, which violates war powers.
The War Powers Act itself I would call unconstitutional, but as for your point, yes I feel the argument for Libya being unconstitutional is strong.
He tried to issue too many recess appointments which were ruled illegal.
He did try to do something that he was unable to do. I suppose it's fair.
He used the IRS as a political weapon. After the Supreme Court ruled in Citizens United, the IRS began holding back conservative PACs. Not all liberal PACs were held back.
Obama was found to have nothing to do with the scandal. Not to mention that the IRS was found to have no political bias in their scrutiny, just that it was unfair. http://www.usatoday.com/story/news/politics/2014/09/05/senate-subcommittee-report-on-irs-tea-party-targeting/15130715/
sources inside the IRS leaked confidential Romney donation information to the Huffington Post during the presidential campaign.
Obama didn't have anything to do with them leaking that information though. This was just more of the IRS fucking up.
He illegally spied on journalist during leak investigations and cracked down heavily on whistleblowers within the government. Many people in the press have called this president the very worst for press freedom EVER.
His actions along these lines are one of my biggest problems with the President. That said, you didn't list anything that he did with regards to this as being unconstitutional.
He is illegally spying on every single American with the NSA, but this could also partly be blamed on Bush.
I blame this much more on the establishment of the Foreign Intelligence Surveillance Court than even Bush or Obama. Even then, it has not been ruled unconstitutional yet and I question whether it will.
He unilaterally issued executive amnesty, something that several law professors said was illegal. Obama, himself, prior to issuing it had said it would be impossible for him to do it, implying there is shaky at best legal ratioinale for the move.
Actually, http://www.washingtonexaminer.com/on-immigration-obama-may-be-cynical-but-hes-not-breaking-the-law/article/2551807, along with a link to the nonpartisan Congressional Research Service http://fas.org/sgp/crs/misc/R42924.pdf, is well within his means. Even the Federal Judge that halted his actions did so not because he called in unconstitutional, but because he wanted questions answered before it was done.