Path to Exile can hit one creature, but Settle the Wreckage will hit all attacking creatures, with a similar effect. White is the primary exiling color, and Dredge doesn't like exile. It's common for Jund midrange decks to run this in the mainboard, never mind the sideboard. And if those cards were creatures, the Ooze's controller can gain life and put a +1/+1 counter on the Ooze. Scavenging Ooze is a classic anti-graveyard card, a 2/2 for 1G that can exile cards at will. But be aware that Ox of Agonas and Conflagrate can hit the Crusader since they are mono-red. Bloodghast, Prized Amalgam and Stinkweed Imp can't handle this card, and Abrupt Decay can't hit it, either.

This isn't the premiere anti-Dredge card, but it can take Dredge players off-guard with its protection from black and protection from green. Some creatures can fight back against Dredge, such as Mirran Crusader. Bojuka Bog is a land that can exile graveyards when it enters the battlefield, and it taps for black mana. In return, it has the classic Leyline effect: it may begin the game already on the battlefield if it's in its owner's opening hand.

This effect practically halves the Dredge deck's firepower, and in black mana, Leyline of the Void has a similar effect, though it's more costly.

In white mana, Rest in Peace is a go-top option against graveyard-based decks, costing just 1W to exile all graveyards and exiling any other cards that would go there.

Modern dredge deck