I really thought a lot about this question, and it's somehow hard to find anything I would call a 'crowning' achievement.
For sure it wasn't things like 50 in a sortie or 300+ killstreaks in a late war perk monster. The greatest singular joyful excitement I ever had was very early on, my first 2 kill sortie, aka 'name in lights'
Other than that.. reaching 1000 tank kills in the Hurri D was worth a celebration as well as shooting down my 100th B-29. (I even made 'look at me' threads about it
). As well as getting the regular "4 B-29 in a sortie" achievement (twice), especially as I don't even see that many B-29s anymore.
Oh, and my best tank shot: Getting a >6k first shot hit and kill. On a friendly outside icon range. Best killshot ever