Answer: Franklin D. Roosevelt
You didn't provide a list of choices, but Franklin Delano Roosevelt issued by far more executive orders than any other president. FDR signed 3,721 executive orders. (Five of them were overturned by the Supreme Court as unconstitutional.)
The next closest presidents in use of executive orders had only half as many as FDR. Woodrow Wilson issued 1,803; Calvin Coolidge issued 1,203; Teddy Roosevelt issued 1,081. If we think presidents recently have made heavy use of executive orders -- such as 277 executive orders by Barack Obama -- they are not even close to the high numbers issued by some presidents in the past.
According to reporting by CNN, President Donald Trump, who had criticized Obama's use of executive orders, is on pace to sign more executive orders than any president in the past 50 years. Trump is averaging over 4 executive orders per month. President Obama's number of executive orders for his eight years in office averaged less than 3 per month.