He shows this in the log:

15:35:00 launcher Preparing to launch minecraft client for 1.12.2
15:35:01 launcher Checking installations.
15:35:01 launcher Minecraft client 1.12.2 is ready to start.
15:35:01 launcher Starting!
15:35:01 launcher Using default game log configuration client-1.12.xml (outputs XML)

And after open the game, the game crashes and shows the message:

Error

An unexpected error has occured and the game stopped to work. We sorry to inconvenience.

Obs: This error happens in all versions.