So what constitutes evil to everyone else? How do YOU define evil in your campaigns/worlds?
For me, it tends towards a combination of the Ends and the Means.
Evil characters can have
any kind of goals (Good, Evil, or in between), though they tend toward Evil goals. But they're ultimately willing to use
any means (including murder, genocide, rape, mental domination, and worship of and sacrifices to dark gods) to get them, regardless of the nobility or ignominy of the final goal. Of course, if they have even a decent intelligence, they also understand that letting those actions be discovered could interfere with said goal.
Good characters
must have non-Evil goals (and usually have fairly Good/noble goals). And they'll try really hard to avoid "Evil" and even
questionable means to achieve them.
Neutral characters generally have non-malevolent goals (could be self-interested or could actually be Good), but are more willing to "break a
few eggs" (stealing, betrayal, blackmail, manipulation, kidnapping) than Good characters, but are rarely willing to go as far as an Evil character (hesitant to use murder/assassination - will almost never use rape and/or sacrifice).
An example:
Kingdom is ruled by an Evil Tyrant.
Evil Goal: Kill him and replace him on the Throne.
Neutral Goal: Overthrow him, maybe kill him if he's a threat, and replace him on the Throne with someone on your side (probably someone that
isn't obviously Evil).
Good Goal: Overthrow him (preferably imprison him) and put a Good person on the Throne or replace the Throne with another, more benevolent, government.
Evil characters can have any of these goals. Neutral characters will probably only have the Neutral or Good goal. Good characters should have the Good goal... though some of them might lean a little close to the Neutral goal overall.
Evil Means: Murder, Assassination, Poisons of any kind, Rampant and even unnecessary Blackmail and Theft, Terrorism, Murder the children of every lord and merchant publicly supporting the Tyrant's rule, Making and Breaking Deals as convenient, Kidnapping the Tyrant's daughter and forcing her to marry him and then consummating that unwilling union.
Neutral Means: Some Poisons (preferably not deadly, but harmful is probably fine), Theft, Exposing Tyrant-supporters despite the harm it may bring them, Kidnapping the Tyrant's daughter to keep the Tyrant from further excesses. Anything more extreme (assassination, blackmail, terrorism, even breaking deals) will probably be kept to a minimum and focused only where deemed absolutely necessary.
Good Means: Inciting Rebellion, Building a Coalition, Minimizing Casualties, Taking Prisoners, Publicly demanding that the Tyrant step down, Offering Public Challenges, Killing only in Self-Defense. Avoiding murder, assassination, blackmail, terrorism, and the worship of dark gods entirely. Keeping theft to a bare minimum and only using sleep/knock-out poisons at the worst - if at all.
Good characters will never use the Evil Means and keep Neutral Means to a minimum. Neutral Characters will use Good and Neutral Means, while keeping outright Evil means to a minimum. Evil characters can use whichever means most suit the way they wish to accomplish their goal.
And, of course, I'm willing to have a little flex here and there. But consistently choosing Evil goals and/or using Evil means? That puts you pretty squarely in the Evil camp, even if your ultimate goal is "Save my people from the Evil Tyrant".