Updated: Dec 15, 2019
Evil can be defined as the action of maliciousness for the sake of maliciousness, or for the sake of causing either harm or mischief. Many acts and people are evil, even if that evilness is not pure evil, i.e, even if maliciousness is just a part of the equation. The thing is it would be most likely that nobody, including me, would define themselves as evil whether we are one or not. It’s stupid to claim one is evil if they are evil, because it can harm one’s reputation, whether they are aware that they're evil and whether they're delusional about them being good, in the form of repression. Am I evil? Nope. Even if I am evil, I won’t admit it.
Forget about the nonesense about villains want to “take over the world”. The desire to conquer the world isn’t necessarily evil. Are the inventors of the internet evil, given that the internet have “conquered” almost the entirety of the human population? Are experienced urban planners evil because they’ve urbanized a very large portion of the globe - and on the way to urbanize more? Is it evil to actualize your potential worldwide? Nope, nothing necessarily malicious about that.
Evil people can be anyone and can be everywhere. It’s not just a dictator of a third-world country, a cult leader, a corrupt politician, and so forth. Evil people can be your average Joe, waiting in the same bus stop as you, offering you coffee, sleeping next to you your bad. A wise evil is one that stays hidden, or at least strives to remain in the shadows and work from there.
Basically, the entry to evil begins when you commit malicious deeds on purpose and on a constant basis. Even if you don’t think so and others disagree, too - you’re evil if you correlate with the previous sentence. Definitions and logic don't care about your opinion, that’s why logic can be very blunt and insensitive… and perhaps be used for evil by those who follow it and declare it in the ears of others. Not me, though.
A good example that I'll refer you to is one of Voltaire's songs (the modern musician), "When You're Evil". He seem to roleplay as an agent of evil standing in the way of everyone, and not only doing it on purpose, but enjoying it as well, not wanting any form of compensation for his "work". Look it up on YouTube, or at least read the song's lyrics, as it's actually a good song and a good example to what I wrote in this article.