As much fun as people have talking about Danny getting the crap beaten out of him and hiding bruises and injuries, I’m not certain ghosts CAN be traditionally injured? At least in the context I’ve built up for Ghost Physics… Like, Danny is essentially injuring himself whenever he rips his face in half to dodge something, or when he forms a spectral tail. If you can atomize and reform your body with no consequence, then physical damage is almost meaningless.
Ghosts are very defined by self perception, so most can be convinced into thinking they’re physically injured and experience pain from it, but the only surefire way to hurt one is by targeting their ectosignature nervous system. Energy attacks seem to be most effective, maybe because the energy can travel through a ghost’s 4D connection to the GZ and stun their nervous system? Disrupting the 4D connection would also work well as a non-physical attack, or on the same note “hijacking” a ghost’s body by overriding the signal from their ectosignature and telling the mass to do something else (probably how the Fenton Thermos works)
Danny definitely gets bruises and injuries in human form, mostly from bullying, I’d imagine… I’m not sure if they’d heal at an accelerated rate on their own, but turning into Phantom or atomizing and reforming his human body could heal them instantly as well, so… Danny is terrifyingly unkillable? The most damage he’s gonna sustain from ghost battles is sleep deprivation and uhhhhhh probably PTSD