The only creatures that avoid Flame Sweep’s damage are those you control with flying. The set of creatures dealt damage includes creatures you don’t control with flying and creatures you control without flying.
Legalitet:
Standard: Ej legal
Pioneer: Legal
Modern: Legal
Legacy: Legal
Vintage: Legal
EDH / Commander: Legal
Pauper: Ej legal
Explorer: Legal
Historic: Legal
Brawl: Ej legal
Premodern: Ej legal
93/94: Ej legal