All spell criticals against you cause 15/30% of the damage taken to the caster as well. The damage caused by Eye for an Eye will not exceed 50% of the Paladin's total health.
Eye for an Eye is a 2 point talent in the PaladinRetribution tree. This talent gives the paladin a chance to reflect a portion of the damage received from magical attacks.
Eye for an Eye can critically strike for 150% of normal damage.
Eye for an Eye cannot be reflected under any circumstance, even if the paladin's spell is reflected and procs it. It will instead strike the enemy that reflected the spell.
Eye for an Eye damage can proc an enemy paladin's Eye for an Eye.
The reflected damage is always dealt as Holy damage, regardless of the school of magic that proc'd it.
With its PvE-oriented redesign in patch 4.0.1, Eye for an Eye no longer has a cap on its damage reflected, but now has a 2 second internal cooldown. Additionally, it can no longer proc off periodic spell damage.
Trivia[]
Eye for an Eye is a common Paladin spell in Hearthstone. The flavor text reads: "Justice sometimes takes the form of a closed fist into a soft cheek."
Patch 4.0.1 (2010-10-12): Eye for an Eye is now a tier 1 talent, down from tier 4, and has been redesigned: All magic attacks against you have a 20/40% chance to cause 30% of the damage taken back to the attacker as well.
Previous talent: All criticals against you cause 5/10% of the damage taken to the attacker as well. The damage caused by Eye for an Eye will not exceed 50% of the Paladin's total health.
Patch 3.2.0 (2009-08-04): Now properly triggered by periodic critical strikes. In addition, the tooltip incorrectly stated that 20% damage is reflected, when it is actually 10%. Tooltip fixed.
Patch 3.1.3 (2009-06-02): This talent now deals 5/10% of the critical strike damage taken by the paladin back at the attacker (down from 10/20%).
Patch 3.0.3 (2008-11-04): No longer breaks crowd control effects.
Patch 3.0.2 (2008-10-14): Now reflects 10/20% damage from all critical hits (was 15/30% from spell critical hits only).
Patch 2.2.0 (2007-09-25): This ability can now trigger while the Paladin is sitting.
Patch 2.1.0 (2007-05-22): Some spells did not trigger Eye for an Eye correctly. That has been fixed.
Patch 1.10.2 (2006-05-03): Will now properly produce its damage effect on the attacking caster.
This talent can now trigger while you are mounted.
If a paladin avoids damage with [Divine Shield], Eye for an Eye will not react.
Patch 1.9.3 (2006-02-07): This talent will now still do damage when the paladin is stunned. In addition, if the critical hit kills the paladin, damage will still be dealt to the spellcaster.
[Eye for an Eye].
Patch 5.0.4 (2012-08-28): Removed. 
[Divine Shield], Eye for an Eye will not react. 
