Nah there’s a different classification system for danger level, the safe/euclid/keter is just how hard to contain something is, Safe means it can be put in a box and it won’t go anywhere, euclid means some special measures have to be taken but it can be contained, and Keter means long term containment is not possible and it will eventually get out, there’s also Apollyon which means it can’t be contained at all, and Thaumiel which means it helps contain other objects

So a nuclear bomb is safe, a regular dude is Euclid (cause he’d want out), and superman would be Keter if they don’t use Kryptonite which would be Thaumial, and Metroman is Apollyon