
Enchantment
Whenever a creature you control enters, it deals damage equal to its power to any target.

Wrong - replace with damage-on-ETB enchantment

Deals damage equal to power when creatures die, similar payoff effect

Nearly identical effect: deals 5 damage when big creatures enter

Symmetric version of the same ETB power-damage trigger

Wrong

Cheaper ETB damage trigger for creatures entering

Wrong

Creature version dealing power-based ETB damage

Deals 2 damage to each opponent when creatures enter

Wrong

Triples damage, pairs perfectly with ETB damage payoffs

Wrong
→ Infinite death triggers, Infinite ETB, Infinite LTB
→ Infinite death triggers, Infinite ETB, Infinite LTB
→ Infinite LTB, Infinite ETB, Infinite death triggers
→ Near-infinite damage, Target opponent loses the game
→ Near-infinite damage, Target opponent loses the game
→ Near-infinite damage, Target opponent loses the game
The creature that entered deals damage equal to its current power to the targeted permanent or player. If it's no longer on the battlefield, its last known existence on the battlefield is checked to determine its power.
Warstorm Surge is the source of the ability, but the creature is the source of the damage. The ability couldn't target a creature with protection from red, for example. It could target a creature with protection from creatures, but all the damage would be prevented. Since damage is dealt by the creature, abilities like lifelink, deathtouch and infect are taken into account, even if the creature has left the battlefield by the time it deals damage.