Curate, connect, and discover
dabi's first kiss is when you run into him in an alleyway while trying to get away from someone following you. he's just there, minding his business. when you approach him, ask him to help (to which he reluctantly agrees), and ends up making out with you with his back towards the street, effectively hiding you (and him bcs his dark clothes) from whoever was following you around.
In any X-men omegaverse au Charles obviously is going to have a mating bite courtesy of Magneto.
Except I lean towards the worldbuilding where mating bites and bonds will wear off in time if they're not actively maintained.
But Charles still spends more time with a mating bite/bond than not because every time it's nearly been long enough or has just been long enough for it to wear off he and Magneto end up working together for one reason or another and by the end of it Charles has a fresh bite and renewed bond.
The timing is actually coincidental (and more a testiment to how often they end up working together) but is still very much the elephant in the room when Magneto inevitably leaves again and they return to being advesaries.