Re: Savage Worlds
You could build Werewolves just like any other race, which would probably make them less super-powered than monsters.
Or, use a background edge:
How about:
Lykanthrophy: When taking a wound or during the full moon, the character must make an immediate Spirit roll. On a failure, they transform into their werewolve form.
The werewolve can change back into human form only if they can focus and calm down for one minute and make a successful spirit roll.
During a full moon night, a transformed werewolve can't transform back.
In werewolve form, they retain their Spirit, but Smarts is lowered two die types, Strength, Vigor and Agility improve by two types.
Their claws and teeth act as natural weapons, causing strength +d4 damage.
Werewolves gain the all-thumbs hindrance and the fleet footed edge.
Hm. Looking at this, it feels off. But it might give you some idea on where to go with this. :-)