Slip Out the Back

Put a +1/+1 counter on target creature. It phases out. (Treat it and anything attached to it as though they don't exist until its controller's next turn.)

Astarion's Thirst

Exile target creature. Put X +1/+1 counters on a commander creature you control, where X is the power of the creature exiled this way.

Deepmuck Desperado

Whenever you commit a crime, each opponent mills three cards. This ability triggers only once each turn. (Targeting opponents, anything they control, and/or cards in their graveyards is a crime.)

Blightbeetle

Protection from green (This creature can't be blocked, targeted, dealt damage, enchanted, or equipped by anything green.)
Creatures your opponents control can't have +1/+1 counters put on them.

Skatewing Spy

{5}{U}: Adapt 2. (If this creature has no +1/+1 counters on it, put two +1/+1 counters on it.)
Each creature you control with a +1/+1 counter on it has flying.

Spider-Man Noir

Menace
Whenever a creature you control attacks alone, put a +1/+1 counter on it. Then surveil X, where X is the number of counters on it. (Look at the top X cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)

Sadistic Glee

Enchant creature
Whenever a creature dies, put a +1/+1 counter on enchanted creature.

Gix's Command

Choose two —
• Put two +1/+1 counters on up to one creature. It gains lifelink until end of turn.
• Destroy each creature with power 2 or less.
• Return up to two creature cards from your graveyard to your hand.
• Each opponent sacrifices a creature with the greatest power among creatures they control.

Jailbreak Scheme

Spree (Choose one or more additional costs.)
+ {3} — Put a +1/+1 counter on target creature. It can't be blocked this turn.
+ {2} — Target artifact or creature's owner puts it on their choice of the top or bottom of their library.

Lazav, Familiar Stranger

Whenever you commit a crime, put a +1/+1 counter on Lazav. Then you may exile a card from a graveyard. If a creature card was exiled this way, you may have Lazav become a copy of that card until end of turn. This ability triggers only once each turn. (Targeting opponents, anything they control, and/or cards in their graveyards is a crime.)

Essence Capture

Counter target creature spell. Put a +1/+1 counter on up to one target creature you control.

Unity of Purpose

Support 2. (Put a +1/+1 counter on each of up to two target creatures.)
Untap each creature you control with a +1/+1 counter on it.

Essence Infusion

Put two +1/+1 counters on target creature. It gains lifelink until end of turn.

Maximum Overdrive

Put a +1/+1 counter on target creature. It gains deathtouch and indestructible until end of turn.

Mer-Ek Nightblade

Outlast {B} ({B}, {T}: Put a +1/+1 counter on this creature. Outlast only as a sorcery.)
Each creature you control with a +1/+1 counter on it has deathtouch.

Unspeakable Symbol

Pay 3 life: Put a +1/+1 counter on target creature.

Ring of Evos Isle

{2}: Equipped creature gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)
At the beginning of your upkeep, put a +1/+1 counter on equipped creature if it's blue.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Unexpected Fangs

Put a +1/+1 counter and a lifelink counter on target creature.

Sapphire Drake

Flying
Each creature you control with a +1/+1 counter on it has flying.

Cannibalize

Choose two target creatures controlled by the same player. Exile one of those creatures and put two +1/+1 counters on the other.