This won't be going off constantly, but if it triggers twice in a game it's more efficient than most attacks you could have been playing, especially for a Justice card. Has anti-synergy with everyone's favorite Thwart event (Clear the Area) and anything else that wants a hero to be finishing off the side schemes.
Not something you want to put in every deck, but if you're playing a deck with some large thwarting allies, it can be good. Best in multiplayer, where you'll see more side schemes arrive and be defeated over the course of the game; you can often set up so that someone's ally gets the finishing blow (doesn't have to be yours!).