At the risk of being repetitive being impeached for Iran Contra is all that would be necessary for him to be seen as a disaster. To summarize what I'm talking about this is a political scandal where:
1) The White House instructed the CIA to run guns to the Contras of Nicaragua
2) In spite of the fact that Congress
explicitly forbade providing any sort of material support or aid to the Contras because they were a bunch of murderous sadists
3) And further sold weapons to Iran, who were much further up on the US shit list in 1985 than they are now, to fund all of this
4) When the proceeds of these highly illegal arms sales, facilitated originally by Israel of all people, were insufficient to meet the needs of propping up the Contras
the CIA decided it would be a gas to dabble in trafficking crack cocaine at the same time as when Reagan was ramping up the Drug War and specifically targeting, you guessed it, crack cocaine.
5) Oh and as a cherry on the shit sundae said Contras were not, as Reagan liked to argue, heroic anti communist freedom fighters
but a bunch of death squads who murdered nuns for fun and were fighting against the legally elected, but a touch too PINK, government of Nicaragua
We're talking a political scandal where the President of the United States signed off on selling weapons to an enemy of the United States to fund a bunch of death squads behind Congress' back barely a decade after Watergate and funded said weapons sales with illegal drug trafficking during the height of a crackdown on illegal drug trafficking all supervised by the CIA.
Because Congress told the White House it was not ok to prop up a bunch of murderers to bring down a legally elected government they didn't like.
That, in my opinion, makes Watergate look like a kid who got caught snooping on his neighbor's wife by comparison. At least Nixon's abuses of power were for an understandable, if unjustifiable, reason. Reagan's shenanigans in Iran Contra were purely to serve an ideological end regardless of the actual human cost or long term consequences with far reaching consequences on a domestic and global scale.