Plague Belcher

Menace
When Plague Belcher enters, put two -1/-1 counters on target creature you control.
Whenever another Zombie you control dies, each opponent loses 1 life.

Noxious Hatchling

Noxious Hatchling enters with four -1/-1 counters on it.
Wither (This deals damage to creatures in the form of -1/-1 counters.)
Whenever you cast a black spell, remove a -1/-1 counter from Noxious Hatchling.
Whenever you cast a green spell, remove a -1/-1 counter from Noxious Hatchling.

Aboroth

Cumulative upkeep—Put a -1/-1 counter on Aboroth. (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)

Shield Sphere

Defender
Whenever Shield Sphere blocks, put a -0/-1 counter on it.

Tenacious Hunter

As long as a creature has a -1/-1 counter on it, Tenacious Hunter has vigilance and deathtouch.

Baleful Ammit

Lifelink
When Baleful Ammit enters, put a -1/-1 counter on target creature you control.

Woeleecher

{W}, {T}: Remove a -1/-1 counter from target creature. If you do, you gain 2 life.

Volrath, the Shapestealer

At the beginning of combat on your turn, put a -1/-1 counter on up to one target creature.
{1}: Until your next turn, Volrath, the Shapestealer becomes a copy of target creature with a counter on it, except it's 7/5 and it has this ability.

Cartouche of Ambition

Enchant creature you control
When Cartouche of Ambition enters, you may put a -1/-1 counter on target creature.
Enchanted creature gets +1/+1 and has lifelink.

Unstable Mutation

Enchant creature
Enchanted creature gets +3/+3.
At the beginning of the upkeep of enchanted creature's controller, put a -1/-1 counter on that creature.

Voracious Hatchling

Lifelink
Voracious Hatchling enters with four -1/-1 counters on it.
Whenever you cast a white spell, remove a -1/-1 counter from Voracious Hatchling.
Whenever you cast a black spell, remove a -1/-1 counter from Voracious Hatchling.

Soulstinger

When Soulstinger enters, put two -1/-1 counters on target creature you control.
When Soulstinger dies, you may put a -1/-1 counter on target creature for each -1/-1 counter on Soulstinger.

Wickerbough Elder

Wickerbough Elder enters with a -1/-1 counter on it.
{G}, Remove a -1/-1 counter from Wickerbough Elder: Destroy target artifact or enchantment.

Shed Weakness

Target creature gets +2/+2 until end of turn. You may remove a -1/-1 counter from it.

Quillspike

{B/G}, Remove a -1/-1 counter from a creature you control: Quillspike gets +3/+3 until end of turn.

Vedalken Anatomist

{2}{U}, {T}: Put a -1/-1 counter on target creature. You may tap or untap that creature.

The Scorpion God

Whenever a creature with a -1/-1 counter on it dies, draw a card.
{1}{B}{R}: Put a -1/-1 counter on another target creature.
When The Scorpion God dies, return it to its owner's hand at the beginning of the next end step.

Serrated Biskelion

{T}: Put a -1/-1 counter on Serrated Biskelion and a -1/-1 counter on target creature.

Sturdy Hatchling

Sturdy Hatchling enters with four -1/-1 counters on it.
{G/U}: Sturdy Hatchling gains shroud until end of turn. (It can't be the target of spells or abilities.)
Whenever you cast a green spell, remove a -1/-1 counter from Sturdy Hatchling.
Whenever you cast a blue spell, remove a -1/-1 counter from Sturdy Hatchling.

Phyrexian Hydra

Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
If damage would be dealt to Phyrexian Hydra, prevent that damage. Put a -1/-1 counter on Phyrexian Hydra for each 1 damage prevented this way.