What does everyone think the most terrifying/disturbing ability to see would be (except for cause fear)

Imo it would be fortify because imagine if you were trying to kill an eagle the size of a 2-3 story house and made it bleed profusely from hundreds of wounds, filled it with enough poison to kill a herd of 50 elephants, just about every bone in its body shattered, parts of its body on fire, other parts frostbitten, and the rest of it slowly melting away when suddenly everything just stops, it's wounds stop bleeding, the poison is gone, every broken bone instantly snaps back together, the fire goes out with not even a burn mark left over, the frostbite disappears, and all the flesh that had melted off instantly repairs itself, and in that same instant its muscles, bones, skin, feathers, claws, beak, and teeth become visibily heavier and tougher but the creatures mobility is completely unaffected and all you can do is struggle and as watch your attacks that had previously caused minor injuries to the beast now do nothing as it bears down on you and kills you instantly.

So yeah that's why I think the fortify ability would be scary 🙂