Reagan's worst was signing the 1986 Act that forever took modern military arms (full auto) out of the hands of ordinary people. The worst infringement of the 2nd amendment ever.
In fairness to President Reagan, the FOPA did also provide some protections to firearm owners which, while they may be scoffed at as unnecessary, are in some cases quite significant.
Without the FOPA, it would be nearly impossible to transport firearms on a cross-country trip without running the risk of getting pulled over in some town that didn't like them. To be sure, the probability of getting searched would have been pretty small (though with today's so-called DUI checkpoints not as small as it should be) but even so, there's no reason law-abiding people should have to take such risks at all.