Saw an interesting question asked on Reddit that I think I'll ask here.
Are there any characters that you didn't appreciate much before playing FE Heroes, that you have obtained a fondness for since you started playing FE Heroes? (OCs are valid too)
For the OCs, Laegjarn, Alfonse, Helbindi and Veronica are my favourites. Laegjarn is easily one of my Fire Emblem best girls in general, and Alfonse is becoming an honest contender for best lord. Veronica is a precious child that the comics gave me an even bigger appreciation for. Helbindi was just an interesting character that I feel they killed off too soon (though I could also say the same about Laegjarn, though my issue there is more how I feel the manner of her death was beyond contrived).
For legacy characters, I really like Minerva and Titania. Love a good powerful, scarlet haired lady, and their VAs are great. I have also enjoyed Xander's utilisation in the story (it's better than his utilisation in Fates' story), and wish we got stuff like that more often. Azura was also one of my least favourite characters in Fates but even I can admit that stuff like that Adrift paralogue was pretty cool in how they used her there (and as a Flier main, Legendary Azura is amazing). Chrom was also my first +10 5-Star unit besides Clair (who was already a favourite of mine in SoV), so I've gained a bit of an attachment based on that.
That about sums up the main ones I think.
A litttle late on this response on my end, but I now have the time to respond to it:
For the OCs, my favorites are Hrid, Laegjarn, Helbindi, and Veronica.
Hrid is more of a guilty pleasure since I mainly like his design and voice, but his development wasn't much compared to a few other OCs. However, I've been liking him as a character too. I was expecting him to be Ephraim 2.0 personality-wise when they first revealed he tried to assassinate Surtr on his own, but he turned out to have a rather nice and chill (pun intended) personality that you wouldn't expect from someone who pulled an Ephraim. He is also quite rational with the suspicions he brings out regarding who the traitor in Book II was. In his dialogue when he joins your party, he does show a lot of regret that trying to assassinate on his own may have not been the wisest choice, especially when his sister Gunthra was killed while he was absent. Even his chemistry with Fjorm is somewhat interesting, at least when learning how him and Fjorm trained together growing up. I'll admit he could've done a lot more in Book II, but I have hopes we'll see him again in the story sometime in the future. I'd love to see him taking initiative as the new king of Nifl!
Laegjarn and Helbindi I like for similar reasons you mentioned. Laegjarn is my favorite Camus in the series because compared to most other Camus's, she has good reasons for doing what she did, and she has a reasonable amount of respect in the way she treats our heroes. As for Helbindi, his chemistry with Ylgr is cute, and his motivation as a character was also quite interesting as someone who acts rough, tough, and climbs the ranks in the Musspel army but also does so for the sakeof his family.
I've been warming up to Veronica with each appearance she makes, and I liked her development in Book II when she applied the lesson she learned from Seth in one of the paralogues to question Surtr's actions. I'm hoping we'll see her again before Book III ends, especially when the trailer and her scene with Loki seemed to point to something they'll do there.
I've also been warming up to Alfonse and Eir in Book III lately to the point they are also on their way of becoming additional favorites, but I'll wait until Book III ends to give my true judgment on them.
Now for the other FE characters that appeared in other games:
As someone that is yet to play the Tellius games, many of the Laguz have quite my interest. Special shoutouts to Tibarn for having a great design and great personality! I really liked his Forging Bonds conversations, which gave me a good grasp at what his character is like.
Julia and Tailtiu also cauht my attention initially for having some nice designs, but after learning more about their characters, I've also gained some appreciation for them in a new light, especially Tailtiu. Her happy and casual personality is a joy to see, but I also can't help but feel sorry for her when learning why she acts like that because of her rather sad past, followed by a very tragic fate for her in Genealogy.