Backstory: You can learn a lot from successful companies in one country that can be translated to another country. Razor Pay did this in India as a Stripe competitor. Stripe services 32 countries, there are other opportunities out there to be the first in another country.
The Idea: A developer based payment solution.
Deep Dive: You would build a payment platform with a robust api and is easy to integrate from a developer stand point. Here's a list of countries where Stipe is available: https://stripe.com/global.
You would have to understand banking and payment laws in whichever country you pick.
Validation: As more people learn to code and online companies need payment solutions, this platform could have a solid hold in small country/niche.
Monetization: You would charge a percentage over processing and the revenue would come at scale.