Allows the user to instantly kill a selected enemy unit, provided that the unit would deal at least 1 damage in battle, not including any post-combat skills such as Savage Blow. This skill is ineffective against certain characters.
Enemies never have Lethality on them in games where they appear where the skill is triggered by stats for balancing reasons.
In the GBA series, there are no generic Assassins because of this.
In both Awakening and Fates, Lethality has the following properties:
Lethality changes the next attack of the user to one-hit an foe, but does not guarantee that it will hit. This means it is possible to avoid the Lethality hit.
If the target is struck by a Lethality hit, Pavise and Aegis can still activate, even though Lethality will always eliminate them.
Triggered guards from a Pair Up in Awakening or a filled Guard Stance in Fates will block the Lethality hit.
Miracle can trigger against a Lethality hit, meaning that a user hit by Lethality can survive if it activates.
If the said unit has Counter or Countermagic (in Fates), since it did not instantly kill the opponent, damage will be returned to the attacker. It is possible for the attacker to die from the reflected damage if it is high enough.
In Awakening, the highest obtainable activation rate for Lethality is 25%. This is obtained with Inigo as Chrom's son, being in the Assassin class with Limit Breaker, which will give him 60 Skill, or 15% activation rate. This is increased to 25% with Rightful King.
In Fates, playable first generation characters can have a minimum 15% activation rate on Lethality with Quixotic, not factoring in their current skill stat. The Avatar and children characters can have a minimum 25% activation rate (also not factoring in their skill stat), as they can learn Hoshidan Unity which stacks with Quixotic and adds an additional 10% activation rate.