Unlucky lucky summons

Honestly? Only really good users of Brave Axe that I know of are Frederick and Cherche. Camilla herself is too slow; and Raven just got a massive improvement over it. Camilla isn't too bad in Flier Emblem; she's a relatively easily available green flier and I've been working on getting a 5*+10 of her. But she's expensive to build because Brave Axe sucks on her; and +Def is hardly her at her best.

I don't really know Cancel Affinity or Ridersbane too well; if I'm being honest. Just about any Lance user with decent Defense could pull off a Ridersbane set, and Cancel Affinity is popular among Archers. Problem is, all the archers that come to mind have more viable B-slots that they want more.

In case you have a +spd Amelia(preferably not -atk as well) there’s a quad build for her that uses the Life and Death/Desperation. It seems like something you shouldn’t do on armored units but she has the stats to back it up. This is just an example, though. Other great users are Winter Lissa(guaranteed quad with Bold Fighter), Winter Chrom(amazingly high attack) and also Bartre(he’s pretty much an infantry Cherche) and Frederick.

As for Mathilda, pretty much any bow/dagger can benefit from CA because they will probably have the upper hand against Raven tomes. Ridersbane is a pretty decent option for DC Effie, although usually outclassed by Berkut’s Lance nowadays. Pretty much any lance unit that has decent attack can run Ridersbane efficiently.

A +atk Frederick is pretty much cavalry Cherche, so that’s an option for you. The only other one that comes to mind is Legion, who has potential for a Brave Axe build, but he’s better with Slaying Axe in my opinion.
I like Ridersbane on DC mixed tanks (notably Effie if you don’t wanna sac up a Berkut for her), but honestly any blue tank works.
As for Cancel Affinity, I think it works well on fast Firesweep Bow units if you have one of those.

Camilla with DC is a beast. Counters all blues and if built right most greens.