The Weaken Psynergy series is a Jupiter Support Psynergy series available in both Golden Sun games which is used to lower the Resistance of one or enemies. It is available to the Apprentice class series and to the Page class series.
Weaken is the first Psynergy in the series. It hits 1 target, costs 4 PP and is learned at level 9. It is used to lower the target's Resistance by 40, up to the maximum of 80.
A fairly staple move to the RPG genre, lowering an opponents resistance can be a useful bit of Psynergy, especially since it does work on most bosses. However, it only lasts for a short period of time, meaning that to make it effective, the increase in damage dealt before it wears off must exceed the damage that could be done through attacking normally. Because of this, casting it immediately prior to summoning, or other such heavy-damage Psynergy, can make Weaken or Enfeeble a valuable asset in the player's arsenal.