If you forgot or missed the MySQL root password, you check this article. This article help you.

Note: You must change tou your apporative folder location you installed the LiveCycle ("C:\Adobe\LiveCycle8.2\").

1) Create a new blank text file:

C:\Adobe\LiveCycle8.2\mysql\bin\reset-root-password.txt

2) Save two lines to the text file:

UPDATE mysql.user SET Password=PASSWORD('newpassword') WHERE User='root';
FLUSH PRIVILEGES;

You must change newpassword to your new password.

3) Stop the "MySQL for Adobe LiveCycle ES " service via "Start Menu -> Control Panel -> Administrative Tools -> Services"

4) Run below command on Command Prompt (cmd.exe):

C:\Adobe\LiveCycle8.2\mysql\bin\mysqld-nt.exe --init-file="C:\Adobe\LiveCycle8.2\mysql\bin\reset-root-password.txt"

5) Start the "MySQL for Adobe LiveCycle ES " service via "Start Menu -> Control Panel -> Administrative Tools -> Services"

6) You can login MySQL using new password.

You may refer to official article about "How to Reset the Root Password"