It has to be AcherSwan!! I love both of them as characters (so happy I got Acheron, looking forward to a Black Swan rerun) and the story teaser of them dancing sealed the ship (★‿★)

For Genshin, my favorite is still CanDehya! I loved their interactions during the Sumeru Archon quest - Candace showed deep understanding in Dehya, cared for her and knew how to talk to her. Not to mention they both look gorgeous (´▽`ʃ♡ƪ)