I'm always a bit skeptical when authors go for the 'pure willpower' route. Like, sure, mental discipline is part of it, but if it's just about thinking really hard, it kind of undercuts the monstrous, involuntary side of being a werewolf. The good stuff, for me, is when control is a skill they have to painfully build, and even then it's shaky. In some books, it's tied to an anchor—a scent, a memory, a person. They focus on that anchor to pull themselves back. Other times, control is linked to pack bonds; a stable pack provides a collective calm that keeps the wolf in check. Lone wolves struggle more, which makes sense thematically.
And then there's the biological angle some stories take, with weird herbs, alchemical potions, or even magical tattoos that act as suppressants. That can be fun, but it risks making the condition too clinical. The best portrayals, I think, keep an element of danger. Even a 'controlled' shifter is one bad day away from losing it. That tension is the whole point.