As an admin, how can i see an already existing group's permission.

[prempal singh]

This question is in reference to Atlassian Documentation: View, create, or delete a group

Ran into a user permission issue. This guy-could-not move a ticket to Epic Link. Another guy-could. Difference was that the Guy-who-could, is a member of a group. 

Now, how do i  find out what additional access the guy-who-could have that i need to provide to the guy-who-could-not.

[Joseph Pitt]

The best thing to do is look at the permission scheme for the project in question. There isn't a way to look at the group and see what permissions it has.