Jungle Wurm

Whenever this creature becomes blocked, it gets -1/-1 until end of turn for each creature blocking it beyond the first.

Hopping Automaton

{0}: This creature gets -1/-1 and gains flying until end of turn.

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 this creature, prevent that damage. Put a -1/-1 counter on this creature for each 1 damage prevented this way.

Chainbreaker

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

Melira, Sylvok Outcast

You can't get poison counters.
Creatures you control can't have -1/-1 counters put on them.
Creatures your opponents control lose infect.

Rhonas's Monument

Green creature spells you cast cost {1} less to cast.
Whenever you cast a creature spell, target creature you control gets +2/+2 and gains trample until end of turn.

Ornery Kudu

When this creature enters, put a -1/-1 counter on target creature you control.

Urza's Avenger

{0}: This creature gets -1/-1 and gains your choice of banding, flying, first strike, or trample until end of turn. (Any creatures with banding, and up to one without, can attack in a band. Bands are blocked as a group. If any creatures with banding you control are blocking or being blocked by a creature, you divide that creature's combat damage, not its controller, among any of the creatures it's being blocked by or is blocking.)

Sylvan Anthem

Green creatures you control get +1/+1.
Whenever a green creature you control enters, scry 1.

Crocodile of the Crossing

Haste
When this creature enters, put a -1/-1 counter on target creature you control.

Lichenthrope

If damage would be dealt to this creature, put that many -1/-1 counters on it instead.
At the beginning of your upkeep, remove a -1/-1 counter from this creature.

Exemplar of Strength

When this creature enters, put three -1/-1 counters on target creature you control.
Whenever this creature attacks, remove a -1/-1 counter from it. If you do, you gain 1 life.

Defiant Greatmaw

When this creature enters, put two -1/-1 counters on target creature you control.
Whenever you put one or more -1/-1 counters on this creature, remove a -1/-1 counter from another target creature you control.

Witherscale Wurm

Whenever this creature blocks or becomes blocked by a creature, that creature gains wither until end of turn. (It deals damage to creatures in the form of -1/-1 counters.)
Whenever this creature deals damage to an opponent, remove all -1/-1 counters from it.

Channeler Initiate

When this creature enters, put three -1/-1 counters on target creature you control.
{T}, Remove a -1/-1 counter from this creature: Add one mana of any color.

Wicker Warcrawler

Whenever this creature attacks or blocks, put a -1/-1 counter on it at end of combat.

Melira's Keepers

This creature can't have counters put on it.

Emerald Medallion

Green spells you cast cost {1} less to cast.

Serrated Biskelion

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