Where do you personally draw the line between "flaws" and "relationship-killers"?

A lot of people say the essence of a genuine, loving relationship is embracing someone to their very core, flaws and all, as well as forgiving their mistakes. But what might be a flaw/mistake that can be put up with or forgiven "for the sake of love" for one... might be a justified reason to call it quits for another. Just to give an example... drug addiction. Some lovers of drug addicts choose to stay with the drug addict because they want to stand by the one they love through thick and thin, for better or for worse... while others leave the drug addict because they can no longer take the pain or "bullsh*t". A less extreme example would be someone with not-so-great hygiene. One person might overlook this because the unkempt person in question is fantastic otherwise, while another might end the relationship because "love is not enough" to fix unpleasant odors or whatever the turn-off may be.