Just Cause
From PCGamingWiki, the wiki about fixing PC games
Issues and Fixes
Just Cause is only able to run in 4:3 mode without modification. To allow any custom resolution, unzip this file in the target game folder and edit the resolution.ini file to set your preferred resolution. All game elements work in widescreen, though cut-scenes, the in-game PDA, and some other elements may appear stretched.