This simple bash scripts helps you to visualize each IAM user's permission detail like this.
-----------------------------------------------------------
| GetUser |
+---------------------------------------------------------+
|| User ||
|+-------------+-----------------------------------------+|
|| Arn | arn:aws:iam::123456789012:user/s3user ||
|| CreateDate | 2018-01-01T20:00:00+00:00 ||
|| Path | / ||
|| UserId | ABCDEFGHIJKLMNOYQRSTU ||
|| UserName | s3user ||
|+-------------+-----------------------------------------+|
------------------
|ListUserPolicies|
+----------------+
------------------------------------------------------------------------
| ListAttachedUserPolicies |
+----------------------------------------------------------------------+
|| AttachedPolicies ||
|+---------------------------------------------+----------------------+|
|| PolicyArn | PolicyName ||
|+---------------------------------------------+----------------------+|
|| arn:aws:iam::aws:policy/AmazonS3FullAccess | AmazonS3FullAccess ||
|+---------------------------------------------+----------------------+|
----------------------------------
| GetPolicyVersion |
+--------+----------+------------+
| Action | Effect | Resource |
+--------+----------+------------+
| s3:* | Allow | * |
+--------+----------+------------+
-------------------
|ListGroupsForUser|
+-----------------+
sh one.sh # shows your own permission details
USERNAME=s3user sh one.sh # you can specify USERNAME
sh all.sh # redirect all users details under created directory 'output'