You would basically have to remodel it. One tricky way would be, if you double tap G you go into edge slide mode, and then if you hit C you get an extension of the slide and that way you can get the beveled vertices back to where they meet up.
Also there is an addon that has a lot of useful tools to unmake this kind of bevel and other things. It’s called Mesh Machine, linking you up:
https://blendermarket.com/products/meshmachine
