Aside from its hilariously unsubtle title, Bullet to the Head (in theaters tomorrow) has one major thing going for it: It's action movie titan Sylvester Stallone's R-rated return to tough guy cinema, the kind that doesn't co-star all of his peers like some weird AARP ad (see: The Expendables and its 2012 sequel). Stallone, looking more grizzled than ever, plays a hitman who's hell-bent on avenging the murder of his partner. Standing in his way is a similarly large but much younger villain named Keegan, played by Jason Momoa.

Fans of HBO's Game of Thrones will remember the Hawaii-born Momoa as the ruthless Khal Drogo from the show's triumphant first season. A far less number of unfortunate people will also recall that he portrayed the title character in the awful 2011 remake of Conan the Barbarian.

In many studio executives' eyes, Momoa was on track to become the heir apparent to guys like Arnold Schwarzenegger and his future Bullet to the Head cast-mate Sly Stallone. That didn't happen, nor, it's safe to say, will it ever.

Momoa isn't alone in such failed efforts, though, as you'll learn by reading up on Hollywood's 10 Worst Attempts to Manufacture the Next Great Action Hero.

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Written by Matt Barone (@MBarone)