Fighter/2nd/Captain

Mettle

Starting from 2nd level, all Heart Containers you gain from this class become d12s instead of d10s—including the one you gained at 1st level.

Your heart point maximum increases by 3, and it increases by an additional 1 every time you gain a fighter level after this.

Duel

Starting from 3rd level, you can use your bonus action to compel a hostile creature within 30 feet of you to focus on you. The target must be able to see you, though it need not be able to understand you. For 1 minute, the creature has disadvantage on attack rolls against creatures other than you. Additionally, each foot the creature moves away from you costs it 1 extra foot of movement.

You can't compel a creature to duel if that creature can't be charmed.