What is the best vacuum stain/carpet cleaner?

My carpet is very dirty because of stains like NyQuil and etc. The point is, the carpet is dirty and I need to remove stains the best way and need to know what the best carpet stain vacuum remover is. Any help?

Getting rid of carpet stains that reappear after I clean them?

I’ve used a heavy duty carpet cleaner, steam mop w/ the carpet attachment, pretty much all the carpet cleaning solutions (expensive, cheap, & in between carpet cleaners), and nothing has worked. Sometimes the stain will go away and then reappear just like it was before in a few days. What gives?! What’s your best carpet stain cleaning advice?