An 'accomplishment' based on the Stroke of a Pen that can be wiped out with another Stroke of a Pen is an illusory 'accomplishment'.  

Successful Presidents have accomplishments that last past their departure from office.   That is the true historical test of a 'legacy'.  

Obama's legacy of cutting a "deal" where  Iran will be able to have  nuclear weapons in 15 years; sending an Armored Brigade to Poland  to threaten Putin 13 days before Obama leaves office for Trump to deal with; attacking Libya, Syria, and Yemen based on the Bush Iraq War vote during the past eight years;  are not what I call 'accomplishments' that anyone should be proud of.