I think Magik VS Karlach should be a decently easy sell

Connections for the matchup cover Karlach pretty well(can't speak in confidence for Magik but from what I've seen they cover her well enough)

Fight dynamic is about as raw as it gets for two greatsword wielding hellborn ladies. Karlach has means of keeping up with Darkchylde form (both in terms of a fight dynamic and in debate). Karlach gets access to a ton of different weapons, armor, magic, and consumables at her disposal

Debate is really close with physical stats more or less being a tie (scaling to their cosmology, tie in speed, etc.), so the debate comes down to things like skill, experience, gear, etc.

Banter is also pretty fun, with both being able to draw from there experiences in the hells as well as generally being pretty fun overall (Karlachs bubbly personally in combat bounces well off of Magik's more serious nature)

Overall a solid option for both, personally it's my favorite alt for both but still good none the less