Lucy uses that whole “we only use 10% of our brains” bullshit to give Scarlet Johansson ridiculous superpowers when she unlocks the other 90%. If only my brain was firing on all cylinders, I could change my hair style and color at will! The faux-science part is pretty awful, and the style of the movie is frequently annoying (lots of effects (visual and sound) and cutaways to other footage during exposition to try to keep things “interesting” but I always find that irritating). I also kinda don’t like the idea that unlocking this brain stuff also makes her an emotionless robot. By about halfway through she’s more powerful than Superman, but fighting common street thugs, and we’re supposed to think they pose any kind of challenge to her at all? And in the end it gets weird in a less-intellectual-2001 sort of way.
It’s not totally bad, she’s hot, and a few of the action scenes are cool, but that’s about it.