Last 20 years?
Here's 15 in the last 15 years:
Killing Bush's social security privatization
An enormous 2009 bailout
Forcing through Obamacare
LGBT in military
Drone warfare in all sorts of countries we're not at war with, even killing US citizens and getting away with it
Extreme control of leaks and crackdowns on whistleblowers in the Obama administration
Massive campaign in the 2012 elections
Paris Accord without Congressional approval
DACA via executive order
Killing the filibuster on judges
Iran deal without Congressional approval
Clear Power Plan via executive order
Net neutrality
Trying to rig the 2016 primaries
Calling Trump's bluff on the government shutdown