List your top fanfic on AO3 for every year, sorted by kudos.
2013: Mistaken Identity (Doctor Who/Harry Potter, 19,806 words, 100 kudos)
When I first started writing in 2013, I posted only on ffnet. I didn't get onto AO3 until April, 2014 and when I finally did, I posted all of my works there so they all are dated around that time. Luckily I can get the real dates from ffnet. Coincidentally, Mistaken Identity was posted on the last day of 2013.
I was (and still am) happy with the reception this fic got, considering that Harry (or Hermione or Ron) do not appear in it at all.
2014: The Actor (Doctor Who RPF, 36,371 words, 231 kudos)
My most popular work ever, mainly because it fills a popular niche that doesn't have many entries - people seem to like stories where actors go to their IP's universe, but there aren't many with David Tennant going to the Doctor Who universe. Looking back on it now, it's embarrassing how poorly it's written. I should go back and fix it. (Same with Mistaken Identity, actually.)
2015: Neighbours (Doctor Who RPF, 37,230 words, 63 kudos)
Now we're getting into more normal kudo levels. Neighbours is one of a series of stories set in an AU built off The Actor (yes, an alternate ending to one of my own stories). The AU seems to have a small pretty devoted following, though I haven't written anything for it in a while.
2016: Blue Rain (Doctor Who superhero AU, 55,144 words, 95 kudos)
This one is surprising, if only because I hadn't realized that it's been three years since I wrote this. This AU is still in my brain (I'm actually working on a story for it right now). In my opinion, this is my best chaptered fic, and that's probably because the plot is entirely original and I took the time to do it right (in contrast to the first two fics above, which I rushed to post, as I was in those heady first-time-writer days).
2017: One Day in a Million (Doctor Who RPF, 9,209 words, 45 kudos)
Another entry in the same AU as Neighbours, this is a set of fluff short stories that I would continue to add to if I felt any inspiration. Like I said, there's a small but devoted set of people who like this AU, oddly enough.
2018: "Tea and Revelations" (Doctor Who AU, 4,012 words, 24 kudos)
By this time, I'm really not writing much, but I'm pretty happy that of the works I posted in 2018, this is the one with the most kudos. This is a Blue Rain story, and that AU does not have a devoted following - but I have a small group of friends who like it and this was a particularly nice story with Sylvia being Sylvia and Wilf being Wilf.
2019: "Jack Reckoning" (Doctor Who, 2,566 words, 51 kudos)
You might have noticed that every story in this list so far has involved David Tennant in some way. I'm nothing if not consistent. However, not a single story I've posted in 2019 so far has involved him (no promises for the rest of the year), and normally my stories that do not involve David Tennant get no attention whatsoever. The only reason why this story has gotten any attention is because everyone (including me!) wants to see Jack Harkness meet the Thirteenth Doctor. So there you are.