Sure. During TBC in WoW, I'd had it with the guilds on our server perpetuating mediocrity with poor recruiting and loot systems, so I decide to form my own with a friend of mine. To advertise the guild, I decided I would go for realm first level 70, since I'd been in both the alpha and beta and knew the zones and quests like the back of my hand. Some people from the top PvE guild on the server were also competing with me and another person from a different guild. I actually got antagonizing tells from one of their officers accusing me of account sharing. Sorry, but it was all coffee, willpower and sleep deprivation.
In any case, I ended up being successful in my quest for realm first level 70. From there, we proceeded to chain run 5-mans and prep for raiding. We did well in Karazhan, though we weren't quite at the top of the server yet. That's what happens when you start out with only ten or so people, not all of whom raided regularly. For Gruul, we climbed up to get the server second kill. We would have had the realm first, but the "top" guild's kill came when Gruul bugged out and wasn't knocking people in the air like he should. So they had an easy time with spreading out and just DPS racing. As for the first legitimate kill, that was ours.
In any case, the same officer who was antagonizing me kept talking shit in their back channels. We had one of their former members by then, because he wanted to be in the top guild. He was relaying all the crap that officer was talking about us. So we did what anyone would do and just proved it with realm firsts. From there, we proceeded to get every single realm first, save one (Illidan, because we'd lost one of our main tanks and had to resort to using a prot pally). Long story short, that officer of theirs eventually quit, but not before wrecking their guild with toxicity. They were never the same again after that, though they eventually transitioned into a decent semi-hardcore guild of nice people after many repairs. But it's rather tragic, because they actually got the reputed first "legit" kill of Onyxia (i.e. non-tauntable) during vanilla. It just goes to show it takes a lot of effort to maintain status as a top guild in the world. Not only do you need good players, but you need good people.