Board Thread:Questions and Answers/@comment-44675188-20200307011234/@comment-39718735-20200629103125

Ultimate Kars' source of immortality is his capability to adapt (that requires some clever thinking from his part as shown with the shell he created to survive the lava). Whenever people speaks about immortality it's hardly ever absolute (DIO brags that since he's a vampire he's immortal and sunlight can easily kill him).

Unless he can adapt by adquiring a stand ability any normal, invisible stand can bash his brain in and he'd not even notice unless as some fans theorize the special elemental abilities the pillar men used were actually stands.

The non-canon novel Jorge Joestar speculates he may be able to copy stand abilities yet it's not conclusive at all since as I said, it's not canon. The ULF manifestates changes over the body, a stand is something rather spiritual... although Araki for some reason put the mask next to the arrow as being stand-granting objects so who knows...