We recently adopted Microsoft Teams as platform for Team Collaboration. As part of adoption there are various experiments that we do like trying out different third-party apps for productivity. In so doing these apps posts messages that might be noise for others and I wanted to delete these messages post uninstalling these apps. But alas, I couldn't delete the messages even though I'm wear the owner role (the other possible role being member) of the channel.
Microsoft Teams by default disables this functionality, perhaps to preserve data integrity.
As Administrator of Microsoft Teams however, you can change this default setting
Step 1: Go to Microsoft Teams Admin Center and login as Admin for Teams.
Step 2: Go to Messaging Policies, and click Add button to create a new policy (you may call it Power-Owner, if you will) where you can turn on the option - "Owners can delete sent messages". See below snapshot for reference:
Step 4: Click Manage users button that you can see in the table navigation to assign this Power-Owner (as I call it) to the select group of users.
Step 7: Celebrate for becoming a Power Owner who can delete others messages. Don't you forget, "With more powers, come more responsibilities!!.."