I got this error while I was triying to create a password file on Oracle 18c database, it initially failed by below error:

OPW-00029: Password complexity failed for SYS user : Password must contain at least 8 characters.

Here is the my orapwd syntax:

[oracle@helios dbs]$ orapwd file=orapwcdb password=here_pass entries=5 force=Y

From oracle documentation

12.2, the default, creates the password file in 12.2. format. This format supports granting administrative privileges to external users and enables SSL and Kerberos authentication for administrative users.

12 creates the password file in Oracle Database 12c format. This format supports the SYSBACKUP, SYSDG, and SYSKM administrative privileges.

so I changed my syntax as below:
oracle@helios dbs]$orapwd file=orapwcdb password=here_pass entries=5 force=Y format=12