Kapow!

Put a +1/+1 counter on target creature you control. It fights target creature an opponent controls. (Each deals damage equal to its power to the other.)

Spider-Man, Miles Morales

Vigilance, trample (Attacking doesn't cause this creature to tap. He can deal excess combat damage to the player he's attacking.)
Whenever Spider-Man enters or attacks, put a +1/+1 counter on each other creature you control. Those creatures gain trample until end of turn.

Forest

Prowler, Misguided Mentor

Prowler can't be blocked by creatures with power 2 or less.
Whenever Prowler deals combat damage to a player, put a +1/+1 counter on another target creature you control.

Kraven's Cats

{2}{G}: This creature gets +2/+2 until end of turn. Activate only once each turn.

Lurking Lizards

Trample
Whenever you cast a spell with mana value 4 or greater, put a +1/+1 counter on this creature.

Venom Blast

Put two +1/+1 counters on target creature you control. It deals damage equal to its power to up to one other target creature.

Spider-Man, Brooklyn Visionary

Web-slinging {2}{G} (You may cast this spell for {2}{G} if you also return a tapped creature you control to its owner's hand.)
When Spider-Man enters, search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Spider-Rex, Daring Dino

Reach, trample
Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)

Scout the City

Choose one —
• Look Around — Mill three cards. You may put a permanent card from among them into your hand. You gain 3 life. (To mill three cards, put the top three cards of your library into your graveyard.)
• Bring Down — Destroy target creature with flying.

Spider-Bot

Reach
When this creature enters, you may search your library for a basic land card, reveal it, then shuffle and put that card on top.

Guy in the Chair

{T}: Add one mana of any color.
Web Support — {2}{G}, {T}: Put a +1/+1 counter on target Spider. Activate only as a sorcery.

Grow Extra Arms

This spell costs {1} less to cast if it targets a Spider.
Target creature gets +4/+4 until end of turn.

Twisted Spider-Clone

When this creature enters, put a +1/+1 counter on each creature you control with a +1/+1 counter on it.