The pinch bolt that holds the camber/caster adjuster in place? If youre having trouble getting that out the bushing itself is going to be a nightmare lol. Replace your ball joints while you're at it, because you're probably going to wreck the upper joints beating them with a hammer to get the adjuster out.
A decent air impact or GOOD cordless impact (i.e. milwaukee fuel, snap on, IR) should get the bolts out easily. Lots of heat and PB blaster wont hurt though.