Anybody completely objective would say Bill Clinton.
Hindsight suggests differently:
1. NAFTA
2. Signed banking "reforms" that did more than anything else to set up the 2008 housing crisis.
3. Forced Ukraine to give all of its nuclear weapons back to Russia as a condition of independence.
4. Having to play defense on the Monica Lewinsky scandal discredited feminist opposition to Trump.
5. Wasted too much time unproductively tilting at social issue windmills that needlessly increased polarization and were ultimately overturned by the other side (Brady Bill, vetoing the partial birth abortion ban, etc.).
And how does that stack up to, among other things, trying to overturn a free and fair election to make oneself dictator of the United States, thereby destroying the country as we know it?