Same issue as well.
I received a response from Valorant's support and this was the highlight of what I got:
"First of all, I would like to thank you for your support on VALORANT and we really appreciate it. Understand that you currently facing the error VAL 128 when try to launch the VALORANT. Don't worry let me take a look on it and see what can we do for you.
In regards to your concern, we are aware of this issue with the error code VAN 128. Apparently, the issue was triggered due to an update launched for AVAST / AVG Anti-Virus and it actually triggered the error code VAN 128. In this case, I would advise you to contact Avast / AVG for further assist to resolve the issue as the root cause lies with them. I hope for your kind understanding and patience regarding this."
I tried to contact and did what I needed to do using the steps given on the issue but it was useless. I am planning to just uninstall AVAST but it won't let me.
And, I don't know what to do anymore. :/