This study investigates the role of gamification elements in driving user engagement within fintech credit applications, addressing a significant gap in understanding their differential effects. Employing a quantitative approach, we surveyed 315 users of fintech credit apps in Vietnam, analysing data through PLS-SEM and Necessary Condition Analysis. Results reveal a hierarchical impact of gamification elements on engagement, with challenges exerting the strongest influence, followed by leaderboards, badges, and points. The study uniquely identifies interaction effects between elements and elucidates the mediating roles of perceived usefulness and enjoyment. These findings advance gamification theory in fintech contexts and offer practical insights for app developers, contributing to the design of more effective, engaging digital financial services that can potentially enhance financial inclusion and literacy.