Just seeing how it has messed up a lot of peoples' lives that were close to me, I would have to say meth. It changes you for the worse. I'm not saying that it does for everyone, but I can say that I have lost 4 or 5 of my best friends back in high school due to meth. They didn't die or nothing, but they ended up in prison or looking like a freak of genetics by missing teeth and just their general appearance.