FFMpeg. But it's command line. The commands are easy once you go through some basic tutorials.

Handbrake

Avidemux ffmpeg is great but.... If anything it's greater for batch conversion, eventually. For conversion testing a la trial and error in order to find the best settings, not so much... Learning curve is going to get steep Besides for filters and general use it's not necessarily going to be more handy than press button with mouse https://en.wikipedia.org/wiki/Avidemux It can hardly be simpler than that https://upload.wikimedia.org/wikipedia/commons/b/bd/Avidemux_2.6.1.png Now it's not suited for big ass movie editing projects, evidently, but that's not what you want I use it mostly for ONE main feature: editing without reencoding. I Cut 10 mins out of a one hour movie for instance, and I export the end result in about 3 seconds, because I don't have to re-encode the whole shit... Nor have to lose quality in the process since the original encoding is left untouched... You can do that too with ffmpeg... But reality is that you get so much options that if you don't have your little file with your pre typed command lines ready to be copy pasted you'll never remember what the right settings were nor what the right command was. unless you typed that for a decade everyday, which won't be the case