IIUC, when fully maxed, this Relic will deal extra damage equal to 100% of the wearer's attack when debuffs are resisted.  So, if you put that on a WuKong with 6K attack, then his A1 will do an additional 6K in damage if the stun is resisted.  

The multiplier on his A1 is already 3.5, so this would be a conditional increase of 28% damage when full maxed out.  Is it just me, or is that just a bit underwhelming.