Words which mean opposite things should have the first letters reflected across the center of the alphabet with the bigger/better version being on the right side…  so instead of min and max, you’d have min and nax.  Endothermic and exothermic?  Which is which, I can’t tell, but call them endothermic and vxothermic and all is clear.  Good and bad?  Yood and bad (or vood and evil, ymmv.)  This is a treat idea.