Xander A slot passive

fury.

Its kind of the default option, but yeah, fury would work well.
On the B slot you could use quick riposte or maybe swordbreaker, so he doesnt get doubled all the time.
Or just go fury/vantage, you can never go wrong with that one.

Default option is Fury. It's the best option, granting him the most wins overall via massive stat boosts. Since he's getting doubled, the -3 damage he's taking per hit perfectly cancels out the damage after combat.

However, if you don't have Fury, here owuld be my next options in order of preference: Attack 3(Gordin 4*, Cecilia 5*), Hp+5 and Defense 3. They grant him nice stat boosts that can win fights; hell, +1 Attack grants him 2 more wins and 1 less loss.

I kinda want to go for life and death and quick riposte