I've been looking for one for a long time and I've found Badaboom to be incredibly bad and Avivo not to be able to run on my GPU (I have an nVidia GPU).
Does anybody know of any other solutions?
I've found an interesting solution: Freemake Video Converter.
It looks like it supports GPU, and I'm currently converting a 2 hours long video (1.36GB). It got to 50% in 10 minutes. Going to share the results in a comment later.