Theodore Roosevelt; by far the precedents he set have had the largest and most negative influence on the growth of our Federal Government both domestic and abroad, the loss of rights for private individuals (to include the lack of property rights; Teddy's support of eminent domain is nothing more than an assertion that all property is communal), and the attacks he began against corporations and capitalism continue to this day.
The last three we've had haven't been great, that is for sure. Clinton benefited from a decent Congress, otherwise he would be in the W/Obama category.