Here we go again with this
Fatalgard has a lot of counters now, a number of which are completely FTP
B-Eirika and the new B-Chrom and B-F-Byleth can all be picked for free and will rip her apart (B-Seliph too, although he may have to use his Miracle if she runs Bonfire). B-Tiki should have no trouble handling her either, easily beating her in Res and cushioning the damage with her Prf B slot. Near Save units like W-Ephraim, A-Idunn, and F-Rhea can handle her on EP. With some investment, even 3-4 Star units like Mininess, Cecilia, NY Kyza, and more can take her on, too.
Then there’s more premium stuff like L-Nanna, both L-Byleths, Legendary and Duo Chrom, and almost anyone running Lethality. There are so many answers to her now that it’s not even funny.