To avenge his mentor?s murder, a former assassin realizes he?s the hunted, setup to achieve their end he must fight his own disenchantment to destroy them before they destroy a founding principle of the country.

I actually think this is actually a step back from the edit Foxtrot25 made to your earlier draft:?To avenge his mentor?s murder, a former assassin must take down the shadow government he used to work for before they destroy the integrity of the country.

My attempt:
While avenging his mentor's murder, a disenchanted?assassin becomes a pawn in a scheme to corrupt the government and must take down those responsible to save his country and clear his name.

Though, I am not sure exactly what a 'disenchanted assassin' is exactly?