What is creatine?
It's a supplement that can boost your energy levels. It's found in meat and your body does produce it, but you would have to eat your way through a fair amount of meat to get enough, so supplementing with creatine makes sense.
As of yet, there have been no studies carried out that have shown a side effect of 'anger' or anything similar. There are always 'horror stories' out there about many supplements, including creatine, but sometimes they are very isolated circumstances, that are often caused by other factors, and sometimes they are even made up.
Creatine, like many things, won't work for everyone, so you have to try it and see if you notice a benefit. But It's safe to say (going by the vast amount of research) that creatine won't cause anger or mood swings by itself.
Lee Gregory Fitness