In the Windows Server operating system, there are several built-in accounts and security groups that are preconfigured with the appropriate rights and permissions to perform specific tasks. (Microsoft)
There are scenarios where testers can obtain full control over members of built-in security groups. The usual targets are members of the "Administrators", "Domain Admins" or "Entreprise Admins" groups, however, other groups can sometimes lead to major privileges escalation.
Below is a table summing up some groups' rights and abuse paths.
Rights and abuses
its members can create and manage users and groups, including its own membership and that of the Server Operators group (e.g. add a member to a group)
its members can also be used to help abuse user accounts with unconstrained delegations since Account Operators can edit users SPNs.
"This group is considered a service administrator group because it can modify Server Operators, which in turn can modify domain controller settings. As a best practice, leave the membership of this group empty, and do not use it for any delegated administration. This group cannot be renamed, deleted, or moved." (docs.microsoft.com)
at the time of writing (12th, April 2021) members can sometimes also escalate through the "Enterprise Key Admins" group and obtain full control over the root domain (read the ADPREP bug).
full admin rights to the Active Directory domain and Domain Controllers
can backup or restore Active Directory and have logon rights to Domain Controllers
its members can sign-in to a server, start and stop services, access domain controllers, perform maintenance tasks (such as backup and restore), and they have the ability to change binaries that are installed on the domain controllers