It seems that the error couldn't start Valorant appears to affect certain Gigabyte motherboards, it's possible that an outdated BIOS or a firmware issue could be causing system instability.
To solve that if you have that model of motherboards, head over to the Gigabyte website and download the latest BIOS for your specific motherboard model (e.g., Z790 GAMING X AX).
Another solution is : right click the file Valorant-Win64-Shipping.exe and select Properties then go to Compatibility tab:
Check the option "Run this program
as administrator" if it's not already checked
Uncheck the option "Run this program
as administrator" if it's checked.
Restart PC and launch Valorant and enjoy playing the game.