20. Storm (X-Men Movies)
The first 'glass cannon' in this list (a character who possesses a lot of power, but no durability at all) is Storm. Storm has the ability to control the weather and her movie feats include making it extremely cold so that Jason Stryker would relent his control over Professor X, zapping the likes of Toad with bolts of lightning and creating multiple whirlwinds to force a pair of Air Force pilots to cease their pursuit of the X-Jet. Essentially, if Mother Nature can do it with the weather, so can Storm. Her weakness lies in the aforementioned fact that no superhuman durability comes with her powerset, so she's as vulnerable as you or I in a fist fight.