I fondly remember playing a game called Horizons.
It was a PVE game, fantasy setting, where all players could master all skills and crafts.
You may think this would get boring fast, but in actuality it lead to very creative ways of doing PvP even though the game did not allow players to even bump into eachother much less strike them with a weapon.
There was the typical train mobs onto your enemy, and the ever popular steal a mobs or steal a resources a player was gathering. But that is mere childsplay.
Where you could do real player vs. player was in competing to finish a world building project before another team could, to add to your personal fame. Since the projects would stay in the world from that time on it was a long term monument to actions YOU took.
There was also the aspect of cornering a market in some crafted item. Someone would be seeling easy to make items at an inflated price, You could them work together with others and flood the market with lower priced items and watch as the first seller depleted his funds buying your cheaper items and re-listing them at higher prices, until he just could not do it anymore and you would continue flooding and finally establish a newer more reasonable price that folks woul dbuy and soon all the other high priced items would disappear.
Then there was the truly gratifying times when a group of macroers would be attempting to farm mobs for some special resource or loot, and because you were much more powerful and faster keep them from getting the mobs by just tagging them all first.
These are forms of pvp that were considered valid in the game Horizons, since you could not directly interact with other players directly. Xsyon has direct interactions between players, so much of what was seen in Horizons as pvp, would be considered griefing here.
( added for clarity : I am not proposing that ANYONE grief another player for any reason. All I am doing here is showing how others found ways to interact with other players in a PVE game that had no direct way to interact or pvp. In Xsyon we have pvp, and the ability to interact directly with players. Grief as it stand is the act of interfering with a players ability to enjoy the game. Examples in Xsyon could include, Verbal abuse that is racist, sexual, or hostile to a players person, removing all trees in an area to prevent players from enjoying crafting or building, paving over junk piles to prevent gathering needed resources. I and My tribe are TOTALLY against such tactics, and will never do such things. Our tribe members are not allowed to grief others in anyway. )
Why must pvp be viewed as just combat?
Here in xsyon, you could just have your tribe work a junk pile in an area that provided some rare item, and then use those resources to become top traders. You could control an area by having a few tribe members start smaller bands and clans associated with your main tribe and "own" an area and still be totally within the rules of the game. You could send roaming hunting parties and gather bones to be the top bone armor crafters. You could try and make you tribe the most popular and have as much control of anything in game that you wanted.
Player vs. player is not only combat and ganking, it is trade, diplomacy, reputations and conduct as well.