Biggest regret in this game?

Probably mine is not throwing all my earliest orbs at greens on the newbie 5%/3% banner for more B.Ike

And maybe promoting the wrong IV of A.Tiki. Not going to be able to fix it for a long time. But it's funny how the speed has come in handy on a few occasions

After that, spending 20 coins on a res+1 seal trying to clear the F.Robin GHB before I knew it was a weekly rotation. Small loss.

And maybe the fact that I don't have Micaiah?

Spending $600 to get a single summer corrin on her first banner last summer, only to basically never use her.

Overall I regret sending home so many 4* units when I first started instead of saving them for merge projects or just making some of them 4* +10.

Specifically though I remember foddering my only Brave Lucina to put Aether on M!Grima because her IV's were terrible and I really liked Grima. In retrospect I probably could have just waited until I pulled a Chrom and promoted him Aether instead. Whoops

Surprisingly, haven't made any major fuck ups.
My biggest regret though is not trying my best in Arena for the first 8 months due to not having a properly built Arena core. Also, not saving my orbs often enough resulting in a pile of huge pity rates unbroken.

My biggest regret is not thoroughly thinking about all the possible units to give the free Close Counter to. I have it to my Henry, but then not long after I was wanting it on Saizo.

My next biggest is probably spending orbs on S!Camilla's and Bridelia's B8% banner. I hardly even use Camilla and I ended up foddering Bridelia for something that I have her... At least I got Hector out of it, so it wasn't a complete waste.

I think the biggest mistake I made was merging all of my Masked Marth at 4-Star, then promoting that for a slightly cheaper 5-Star version. I could have had a Masked Marth +6 by now, instead of a +2. (I wasn't able to get her 5-Star version last year because I was too busy studying for Final Exams around the time of the first Tempest Trials.)

When I thought it'd be really cool to fodder a Hector to put Distant Counter on my free B!Ike, only to have to choose between either inheriting that DC or SB on another, much better unit and having to lose the other skill :'(

A year ago at 3am after getting out of a double shift from work and downloading the FEH game app by accident, half awake, not lucid at all, and passing out on my couch only to wake up the next morning not remembering how I came across this game on the google play store and getting sucked into one of the absolute worst things ever that has ruined my life by robbing me of one the most important necessities:

Time
(and money here and there)

Not saving all my Legion copies to promote and merge into my main Legion. I didn’t understand merging and how it works in the beginning and I wish I didn’t make my Legion suffer for it.

This...

Killing off W!Robin for Brazen Atk/Spd 3.

Foddering DC to B!Ike.... Hopefully I won't regret foddering DC to Myrrh.

Not verifying the IV's of the Fae I had just gotten before merging her into my actual merged Fae and not being able to know now if they were better IV's. This will haunt me for the rest of my life.