Friday Night Funkin' got pretty huge for a while there. Open source, too (not sure about the license) https://github.com/FunkinCrew/Funkin

All games by Shiro games (founded by Nicolas Cannasse, creator of Haxe) : https://en.wikipedia.org/wiki/Shiro_Games

Dead Cells, Papers Please, Dicey Dungeons

Northgard, not an amazing game to me, but successful nonetheless.

Defender's Quest is a little famous, though not enormously famous.

Dead cells is the most recent and prominent example.