It can be anything : a kill, an evasion, a strategical or fleet command choice, a genial trade, great takling, or exploration, a gank, a long plot success, something that when you recall about it you feel proud of ?
For me it was being part of an Arena event winners. It was a FFA 1v1v1v1 and I exactly had a 1:4 win ratio so it means I was not too bad (I used to check every opponent zkillboard after a fight and I believe people participating in it are mostly good fighters).
I really invested a lot of time, efforts and isk (which in the end was an acceptable loss with the profit you get from it and the loot) and I may sound silly or naive, but winning these stupid skins which are all the same give a unique feeling when I see it and know we are only 100hundred to have
Removing the CODE Fortizar and two Astrahus in Niarja, which made it so that CODE did not have a single structure in hisec at the time, was funny that they claimed to hold hisec and yet could not even keep their structures alive.
Ooof - I don’t think many people who haven’t done it can appreciate what it takes to maintain hole control for 72 hours - and I didn’t even put in half as much effort as those in my alliance/corp who were doing the organisation side of it and that was enough.
When I “won” a 1v1 versus a navy cruiser as a navy frigate without even firing a single shot.
It had agressed me right outside an Archangels station in nullsec and it was 100% one-sided, as i couldn’t even reach him. So I locked him up while he was hitting me and flew around the station as a joke, knowing I could dock up at any moment.
After about 20 seconds though, diamond archangel rats warped to the station, landing a few kilometers from our position. Little did he know that I have very good standings with Archangels and so the rats instablapped him while I laughed all the way to his wreck.