Ibuprofen isn't free of side effects either. My understanding was that the biggest risk of Acetaminophen is that it's easy to overdose and it's relatively safe

Ibuprofen isn't free of side effects either. My understanding was that the biggest risk of Acetaminophen is that it's easy to overdose and it's relatively safe when one knows that and stays well below the safety limits (and likely with less side effects than ACC and Ibuprofen). But the bottom line is probably that all painkillers have risks and one should avoid taking too much of them and consult a doctor if one takes them on a regular basis.