To me, that's simple. It's the evil that expands and crams itself down your throat, whether or not you're willing to work with it. It's the kind that works under the guise of Good, but enforces the rules it makes onto everyone, burning away their freedom and their individuality. It's the kind of evil that springs from fear, paranoia, and egotistical lusting after power, rooted in things that were originally meant to be of good purposes, fueled by the stupidity of those who fall to the lure of it, and made unstoppable by the guile and stealth it uses. It's the Big Brother kind of evil, the Illuminati kind. The war of conquest only comes after it pacifies and makes such things seem trivial and not worth paying much attention to, and it lies and manipulates the truth to twist the world the way it sees fit.
That's pure evil.
It's the death of wonder, hope, and magic, the end of freedom, hope, and honor, the final tolling note in the funeral march of wonder and individuality.