You have to take a lot at one time, or chronic overdoses, to damage your liver.
Taking the maximum daily recommended dose (4g per day, thereabouts, in 1g doses) every day for months on end is fine and won’t do any damage.
I’m sorry about your friend but his experience is unrelated to the fact that using the medication as recommended, even long term, is not harmful in the least.
It's a common failure mode and most other OTCs won't kill you if you occasionally accidentally take an extra dose or two. Agreed that it's safe at the correct dose but the hazards are severe and dosing incorrectly is inevitable at population scale.