Level 3
Makeshift Claws.
You gain Advantage when spending Stamina on Slashing weapon attacks.
(1/round) On hit against a Frightened creature, gain STR Stamina.
Natural Predator.
(1/round) When you hit a creature adjacent to an ally, it becomes Frightened of you until the end of your next turn if it fails a WIL save (DC 10+STR).
Level 7
Art of Frenzy.
While Bloodied, you can make an opportunity attack without the usual Disadvantage. Gain STR Stamina on hit, or 2×STR Stamina on crit.
Level 11
Second Chance.
(1/Safe Rest) When you're reduced to 0 HP, remain at 1 HP until the start of your next turn; at which point, you gain STR d8 temp HP (lost at the end of the encounter or when you recover HP).
(1/turn) While you have this temp HP, you can make one attack for free.
Level 15
Primal Fortitude.
When you gain Stamina at the end of your turn, gain 2×STR Stamina instead.