Arguably HTML5 and JS to get both in a state where Flash wasn't needed. Not just for what Flash is famous for either. I used it a lot for "copy this text in a div to the clipboard" when browsers were all over the place on support for that.
TypeScript, I'd say.
Also TC39's efforts in all of JavaScript just about ever since. ActionScript's ES4 efforts left a lot of scars and that "lost version" of JavaScript is quite influential in the very least for how much ES2015+ avoids ES4/ActionScript ideas/problems/concerns as much as it learns from them and eventually reincorporates some of them.