Worstgen
Elder Lee Hung
If I’m being honest, Diamond shouldn’t be *that* hard to break lol. Scratch? Yes. Break? Trained Jewelers can crack Diamond with hammers lol.
Monkey D. Luffy
In the One Piece verse, diamond is one of the hardest substance.
Sentinel
Well, he's right on this one though. Diamond doesn't make you immune to damage, otherwise it wouldn't be possible to cut diamond with a high pressure waterjet irl. It makes your body ridiculously durable, yes, but not immune.