The concept of buying low in fantasy can be a tricky one to navigate. Whether or not you're truly buying low can depend on the size of your league, and how savvy your competitors are. You might have free-agent budgets to consider, or an intransigent owner who won't trade the guy you want, even with a strong offer.
Best we can do is dig up a few players having regrettable seasons, factor in their reputations, then sort them by three categories: buy low, buy lower, and buy lowest. Think of the buy-low players as waiver pickups or trade possibilities in standard (12-team) mixed leagues, on down to target guys in 20-team mixed, or AL-/NL-only leagues.
Here are your nominees: