Sickle Ripper

Wither (This deals damage to creatures in the form of -1/-1 counters.)

Chainbreaker

Chainbreaker enters the battlefield with two -1/-1 counters on it.
{3}, {T}: Remove a -1/-1 counter from target creature.

Past in Flames

Each instant and sorcery card in your graveyard gains flashback until end of turn. The flashback cost is equal to its mana cost.
Flashback {4}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Corrosive Mentor

Black creatures you control have wither. (They deal damage to creatures in the form of -1/-1 counters.)

Slinking Giant

Wither (This deals damage to creatures in the form of -1/-1 counters.)
Whenever Slinking Giant blocks or becomes blocked, it gets -3/-0 until end of turn.

Rustrazor Butcher

First strike
Wither (This deals damage to creatures in the form of -1/-1 counters.)

Argentum Armor

Equipped creature gets +6/+6.
Whenever equipped creature attacks, destroy target permanent.
Equip {6}

Lux Cannon

{T}: Put a charge counter on Lux Cannon.
{T}, Remove three charge counters from Lux Cannon: Destroy target permanent.